COLLEGE  OF  PHARMACY 


"* 


THE   POLARISCOPE    IN   THE 
CHEMICAL   LABORATORY 


THE  POLARISCOPE 


IN    THE 


CHEMICAL  LABORATORY 


AN   INTRODUCTION    TO    POLARIMETRY   AND 
RELATED   METHODS 


BY 


GEORGE   WILLIAM    ROLFE,   A.M. 

INSTRUCTOR  IN   SUGAR  ANALYSIS   IN  THE  MASSACHUSETTS   INSTITUTE 
OF  TECHNOLOGY 

California  College  of  Pharmacy 


g  0rfe 
THE   MACMILLAN   COMPANY 

LONDON:  MACMILLAN  &  CO.,  LTD. 
1919 

*Q 

All  rights  \rtserved 


COPYRIGHT,    1905, 
BY  THE   MACMILLAN    COMPANY. 


Set  up  and  electrotypcd.      Published  September,  1905. 


J.  S.  Gushing  &  Co.—  Berwick  <fe  Smith  Co. 
Norwood,  Mass.,  U.S.A. 


PREFACE 

THE  immense  importance  of  the  sugar  industry  in  world 
economics  has  forced  the  development  of  the  polariscope 
into  a  sugar-testing  instrument  of  high  efficiency.  Com- 
paratively few  practicing  chemists  are  familiar  with  any 
other  application  of  this  useful  laboratory  tool. 

Many  books  have  been  written  on  commercial  saccha- 
rimetry,  but  it  is  only  by  hunting  through  the  whole  mass 
of  literature  of  analytic  chemistry  that  occasional  instances 
can  be  found  of  the  application  of  the  polariscope  in 
general  laboratory  practice. 

Landolt's  great  work  is  the  only  one  devoted  to  a  com- 
plete treatment  of  the  subject  of  polarimetry,  but  that  is, 
in  the  main,  a  book  for  the  physical  chemist  and  trained 
investigator  in  pure  science. 

Hence  I  have  ventured  to  write  a  simple  introductory 
treatise,  not  a  complete  manual  of  polarimetry  by  any 
means,  but  one  explaining  in  an  elementary  way  funda- 
mental principles  and  their  application  in  general  labora- 
tory practice. 

Naturally,  I  have  devoted  much  space  to  methods  in  use 
in  sugar  manufacture,  but  have  also  described  those  used  in 
brewing,  the  starch  industries,  and  food  and  drug  analy- 
sis as  well.  It  has  seemed  best  to  introduce  outlines  of 
some  technical  processes  and  factory  methods  of  chemical 
control  to  make  the  subject  clearer.  I  have  also  over- 
stepped the  strict  bounds  of  polarimetry  to  explain  methods 
obviously  accessory  to  many  determinations. 

v  4; 


vi  PREFACE 

A  sketch  of  the  use  of  the  polariscope  in  pure  science  is 
given  in  view  of  the  great  possibilities  of  the  instrument  in 
that  field. 

In  short,  with  an  experience  covering  nearly  twenty 
years  as  technical  chemist  in  the  sugarhouses  of  the 
West  Indies,  in  the  glucose  industry  of  the  West,  and  as 
a  teacher  of  polarimetric  methods  in  a  great  technical 
school  I  offer  the  book  in  the  hope  that  it  may  prove  a 
guide  to  a  better  comprehension  of  the  polariscope  as  a 
practical  laboratory  tool,  and  suggest  means  of  wider 
application. 

I  can  make  but  small  return  here  in  acknowledging 
my  indebtedness  to  those  who  have  kindly  assisted  me 
in  the  preparation  of  these  pages,  —  to  my  father,  Dr. 
W.  J.  Rolfe,  whose  criticism  and  advice  has  been  an 
inestimable  aid  in  putting  this  book  through  the  press; 
to  Professor  F.  H.  Storer,  an  esteemed  critic,  but  more 
than  all,  one  whose  kindly  interest  and  encouragement 
have  greatly  heartened  me  in  my  task ;  to  my  colleagues, 
Professors  Wendell,  Noyes,  Gill,  Mulliken,  Mr.  A.  G. 
Woodman,  and  others  who  have  aided  me  with  advice 
and  criticism  in  their  special  fields  of  work. 


CONTENTS 

PAGE 

FUNDAMENTAL  PRINCIPLES i 

THE  POLARISCOPE 15 

THE  SACCHARIMETER 28 

ACCURACY  OF  SACCHARIMETER  MEASUREMENTS       ...  39 
GENERAL  NOTES  ON  APPARATUS  AND  LABORATORY  MANIPU- 
LATION ...                                                               .48 

NOTES  APPLYING  TO  SPECIAL  INSTRUMENTS      ....  68 
POLARIZATION    OF     CANE     SUGAR  —  GENERAL     COMMERCIAL 

METHODS 87 

DETERMINATION   OF    SUCROSE  IN  PRESENCE   OF   OTHER   OP- 
TICALLY ACTIVE  SUBSTANCES  (DOUBLE  POLARIZATION)    .  101 

SUGARHOUSE  AND  REFINERY  METHODS Ill 

CHEMICAL  METHODS  OF  DETERMINING  SUGARS        .        .        .160 

STARCH  AND  STARCH  PRODUCTS 173 

MISCELLANEOUS  SACCHARINE  PRODUCTS 222 

APPLICATION  OF  THE  POLARISCOPE  IN  SCIENTIFIC  RESEARCH  .  238 
APPLICATION  OF  THE  POLARISCOPE  TO   CHEMICAL  ANALYSIS 

OTHER  THAN  CARBOHYDRATE  DETERMINATIONS         .        .  260 

APPENDIX 279 

TABLES 285 

INDEX ,        .        .        .  315 


THE    POLARISCOPE    IN   THE 
CHEMICAL   LABORATORY 

FUNDAMENTAL   PRINCIPLES 

The  Function  and  Scope  of  Optical  Analysis.  —  The 
methods  of  analysis  to  be  described  are  based  on  the 
behavior  of  "  polarized  light "  in  passing  through  sugar 
solutions.  In  many  cases  these  methods  can.be  applied 
as  well  to  other  "  optically  active  "  compounds  that  are  in 
the  liquid  state  or  in  solution.  Many  organic  substances 
show  optical  activity  —  about  seven  hundred  have  been 
studied:  hydrocarbons,  such  as  diamyl;  alcohols,  as 
dichlorhydrin ;  acids,  like  tartaric ;  alkaloids,  as  nicotine ; 
essential  oils,  as  oil  of  lemon ;  and  terpenes,  like  camphor. 

Comparatively  little  is  known  about  the  relationship  of 
optical  activity  to  the  chemical  and  physical  structure  of 
matter.  Pasteur,  about  1850,  pointed  out  that  the  optical 
behavior  of  solutions  of  isomeric  forms  of  tartaric  acid 
could  be  foretold  by  a  study  of  the  planes  on  the  crystals 
of  these  acids.  This  relation  has  been  found  to  hold  true 
in  case  of  other'  organic  crystals.  An  analogous  law  had 
been  discovered  in  quartz  crystals  by  Herschel,  in  1835. 
Van't  Hoff  and  Le  Bel,  in  1874,  showed  that  differences 
in  the  optical  activity  of  isomers  could  be  explained  by 
a  peculiar  molecular  structure  and  demonstrated  by  the 
graphic  symbolism  ordinarily  used  in  interpreting  organic 


2  FUNDAMENTAL  PRINCIPLES 

reactions.1  This  theory  has  been  useful  in  predicting  the 
existence  of  many  organic  compounds,  and  may  be  said 
to  form  the  basis  of  the  scheme  of  Fischer's  masterly 
researches  on  the  sugars.2 

While  it  is  not  the  province  of  this  book  to  go  into 
an  elaborate  exposition  of  the  properties  and  theories  of 
polarized  light,  it  is  necessary,  for  the  intelligent  use  of 
apparatus  and  the  understanding  of  methods,  to  describe 
a  few  simple  experiments,  with  brief  explanations. 

Double  Refraction.  —  "Iceland  spar,"  a  crystallized  cal- 
cium carbonate,  which  in  the  natural  mineral  readily  splits 
up  into  colorless  rhombohedrons,  is  the  customary  material 
used  in  optical  instruments  for  producing  plane  polarized 
light.  Looking  through  such  a  rhombohedron  of  Iceland 
spar  in  any  direction  (except  parallel  to  a  line  joining 
the  two  most  obtuse  solid  angles,  known  as  its  "optical 
axis  ")  it  will  be  noticed  that  the  images  of  objects  are 
doubled.  Evidently  the  light  passing  through  the  crystal 
follows  two  paths.  This  "double  refraction"  is  character- 
istic of  any  crystal  not  "  isometric  "  in  structure,  but  any 
transparent  solid,  ordinarily  not  doubly  refractive,  glass  for 
instance,  will  show  double  refraction  if  different  parts  are 
subjected  to  unequal  pressure,  thus  producing  variations 
of  density. 

The  Nicol  Prism.  —  In  a  substance  showing  double  re- 
fraction, each  member  of  the  divided  beam  in  its  passage 

1  A  review  of  the  work  of  Pasteur  and  bibliography  of  original  papers 
will  be  found  in  Landolt's  "  Das   optische  Drehungsvermogen,"   p.  40.     A 
similar  review  of  the  work  of  Van't  Hoff  and  Le  Bel  begins  on  p.  43  of  the 
same  work.     Pasteur's  original  paper  has  also  been  recently  published  in  the 
"  Alembic  Club  Reprint,"  No.  14. 

2  Outlined  by  Tollens,  "  Handbuch  der  Kohlenhydrate,"  II,  1 1-40. 


FUNDAMENTAL   PRINCIPLES 


through  the  crystal  has  undergone  a  remarkable  change, 
known  as  " polarization,"  which  makes  it  available  in  sugar 
analysis.  To  utilize  this  property  it  is  necessary  to  isolate 
one  of  these  beams,  which  can  be  done  by  a  "  Nicol  prism," 
so  called  from  its  inventor. 

Such  a  prism  is  made  from  a  rhomboidal  piece  of  Ice- 
land spar,  one  whose  length  is  approximately  three  times 
its  breadth,  by  grinding  and  polishing  the  end  faces  so  that 
they  make  an  angle  of  68°  with  the  long  edges  instead  of 
the  71°  of  the  original  crystal,  and  cutting  the  crystal  in 
halves  along  a  plane  passing  through  one  of  the  most 


OF  UNPOLARIZED 
a      UGHT 
.CEMENT  JOINT 


FIG.  i.  —  DIAGRAM  SHOWING  PATHS  OF  LIGHT  RAYS  IN  A  NICOL  PRISM. 

obtuse  solid  angles  of  the  prism  90°  to  the  modified  end 
faces.  The  cut  surfaces  are  polished,  and  cemented 
together  with  Canada  balsam,  restoring  the  two  parts  of 
the  crystal  to  their  original  positions.  The  long  side 
faces  of  the  prism  are  blackened. 

Any  ray  of  light  on  entering  a  Nicol  prism  in  a  direction 
parallel  to  the  long  edges  is  divided  into  two  components. 
The  component  most  refracted,  known  in  this  case  as  the 
"  ordinary  ray,"  meets  the  balsam  sheet  at  such  an  angle 
that  it  is  totally  reflected,  and  practically  all  absorbed  by 
the  dark  coating  of  the  sides  of  the  prism.  The  other  ray, 
called  the  "extraordinary,"  striking  the  balsam  plane  at  a 


4  FUNDAMENTAL  PRINCIPLES 

lesser  angle,  passes  through  the  prism,  emerging  in  a  con- 
dition which  is  known  as  "plane  polarized/'1 

Properties  of  Plane  Polarized  Light.  —  Looking  through 
two  Nicol  prisms  at  any  source  of  light,  holding  the  prisms 
so  that  the  light  will  pass  through  each  successively,  and 
revolving  one  slowly  on  its  long  axis,  —  that  is,  around  the 
line  of  direction  of  the  light  beam,  —  it  will  be  noticed 
that  the  light  seen  through  the  prisms  varies  continu- 
ally as  the  prism  turns.  At  certain  points  in  the  revo- 
lution of  the  prism,  180°  apart,  no  light  passes,  while  at 
exactly  midway  between  these  positions  (90°  from  them) 
most  light  is  seen.  As  the  prism  is  revolved,  the  light 
increases  up  to  a  maximum,  and  then  decreases  till  the 
point  of  "  total  extinction  "  is  reached.  Hence,  the  amount 
of  light  passing  through  such  a  combination  of  Nicol 
prisms  in  the  manner  described  depends  on  the  angle 
through  which  one  of  the  prisms  is  rotated  from  the 
positions  giving  maximum  or  minimum  illumination.  The 
relative  positions  of  the  Nicols  giving  maximum  light 
intensity  will  be  found  to  be  that  point  of  rotation  when 
the  rhomboids  of  the  end  faces  are  parallel,  each  edge  of 
the  end  face  of  one  prism  to  the  corresponding  edge  of  the 
other  prism.  When  one  of  the  Nicols  is  rotated  to  a  posi- 
tion 90°,  no  light  passes,  and  the  field  is  dark.  In  the  first 
case,  the  prisms  are  said  to  be  "parallel,"  in  the  second 
"crossed." 

Polariscope.  —  If  the  combination  of  prisms  as  described 
is  held  in  some  suitable  apparatus,  one  prism  being  fixed, 
the  other  capable  of  rotation,  a  measuring  device  can  be 

1  Some  modified  forms  of  the  Nicol,  designed  to  increase  its  light  capacity, 
are  described  in  Landolt's  work  already  referred  to. 


FUNDAMENTAL   PRINCIPLES  5 

attached  to  the  rotating  prism  and  these  phases  of  light 
intensity,  or  light  effects  depending  on  them,  can  be  re- 
ferred to  definite  points  on  a  scale.  Such  an  instrument 
is  called  a  "  polariscope,"  and  can  be  utilized  in  sugar 
analysis.  A  sugar  solution,  placed  between  the  prisms  in 
such  a  way  that  the  light  passes  through  it  in  its  passage 
between  the  prisms,  affects'  the  intensity  of  the  light,  so  that 
it  will  be  necessary  to  rotate  jthe  movable  prism  to  restore 
any  light  effect  shown  by  the  polariscope  previous  to  the 
insertion  of  the  solution.  The  magnitude  of  the  angle 
through  which  the  prism  must  be  rotated  to  restore  the 
original  light  effect  is  found  to  depend  directly  on  the  con- 
centration of  the  sugar  solution,  and  therefore  can  be  taken 
as  a  measure  of  the  sugar  itself. 

Undulatory  Theory.  —  The  so-called  "  undulatory  "  or 
"wave"  theory  has  proved  indispensable  for  interpreting 
these  phenomena  of  polarized  light.  In  its  simplest  form 
this  theory  assumes  that  all  light  rays  are  caused  by  waves 
of  energy  transmitted  in  straight  lilies  through  a  medium, 
called  "  ether,"  which  pervades  all  space,  even  dense 
solids. 

The  transmission  of  energy  in  transverse  waves  propa- 
gated in  straight  lines  can  be  admirably  illustrated  by 
means  of  a  stretched  elastic  cord.  If  one  end  of  such  a 
cord  is  vibrated  transversely  by  shaking  it  at  right  angles 
to  the  direction  in  which  the  cord  is  stretched,  waves  will 
pass  along  the  cord,  as  each  particle  is  successively  set  in 
oscillation.  Obviously  it  is  the  disturbance  that  travels  as 
a  wave  and  not  the  matter  in  the  cord  itself,  each  particle 
of  which  is  merely  oscillating  backward  and  forward.  If 
the  cord  is  continuously  shaken  in  different  directions 


6  FUNDAMENTAL  PRINCIPLES 

transverse  to  its  length,  it  illustrates  well  the  theoretical 
conception  of  ordinary  light. 

The  direction  in  which  the  cord  is  stretched  is  the 
straight  line  which  determines  the  path  of  transmission  of 
the  waves  and  corresponds  to  the  light  ray.  The  particles, 
always  oscillating  transversely,  but  whose  planes  of  vibra- 
tion are  continually  changing  their  position  in  space, 
illustrate  the  ether. 

For  such  a  series  of  transverse  waves  see  the  diagram. 
Two  particles  moving  in  the  same  direction  at  the  same 
time,  such  as  A  and  Bt  are  said  to  be  in  the  "  same  phase.'* 


FIG.  2. 

When  the  displacement  and  motion  of  the  two  vibrating 
particles  are  exactly  opposite,  as  A  and  C,  they  are  said  to 
be  in  "  opposite  phase."  A  "  wave  length  "  is  the  distance 
along  the  line  of  transmission  between  the  two  nearest 
particles  in  the  same  phase,  as  from  A  to  B.  The  distance 
from  one  particle  to  the  next  in  opposite  phase  is  half  a 
wave  length.  A  ray,  representing  the  direction  of  trans- 
mission (path),  of  the  energy  is  a  geometric  line  and  hence 
has  but  one  dimension.  A  multitude  of  rays  having  a 
common  direction  is  called  a  "beam,"  and  can  be  con- 
sidered to  occupy  space.  These  terms  are  also  loosely 
used  by  many  writers  on  optics  to  express  the  waves  of 
energy  themselves  which  are  moving  in  a  ray  or  beam. 

The  color  of  the  light  depends  on  the  period  of  vibration 
of  its  waves.  In  the  passage  of  the  light  through  any 
homogeneous  medium,  as  air,  its  color  bears  a  direct 


FUNDAMENTAL   PRINCIPLES  7 

relation  to  its  wave  length.  Light  consisting  of  waves  of 
one  length  is  said  to  be  "homogeneous'*  or  "  monochro- 
matic," its  color  being  expressed  mathematically  in  terms 
of  its  wave  length  when  passing  through  air.  Light 
made  up  of  vibrations  of  many  wave  lengths  is  said  to 
be  "  compound " ;  ordinary  day  or  lamplight  is  of  this 
nature. 

[See  Preston's  "  Theory  of  Light "  for  a  full  explanation 
of  wave  propagation  and  exposition  of  the  undulatory  theory 
in  its  application  to  optics.] 

Reverting  to  the  phenomena  observed  with  the  two 
Nicols :  when  light  enters  a  Nicol  prism,  owing  to  the 
molecular  structure  of  the  calc-spar,  the  ether  is  prevented 
from  vibrating  in  varying  planes,  its  oscillations  being  con- 
fined to  two  at  right  angles  to  each  other.  Application 
of  the  law  of  resolution  of  motions  will  greatly  assist  in 
understanding  the  theoretical  explanation  of  these  light 
phenomena.  Many  of  the  effects  of  Nicol  prisms  can  be 
made  clear  by  making  a  diagram  of  the  vibration  planes 
according  to  the  doctrine  of  the  "  parallelogram  of  forces." 

In  the  Nicol  prism,  the  theory  shows  that  the  planes  of 
vibration  of  the  two  light  beams  are  determined  by  the 
diagonals  of  the  end  faces.  It  has  been  shown  how  one  of 
these  beams  has  been  disposed  of  by  total  reflection.  The 
plane  of  vibration  of  the  unextinguished  (emerging)  beam 
is  parallel  to  a  plane  passing  through  the  shorter  diagonals 
of  the  end  faces  of  the  prism.  A  plane  at  right  angles  to 
this  is  known  as  the  "  plane  of  polarization."  The  rays  of 
the  emerging  beam  from  a  Nicol  prism,  after  emergence, 
continue  to  vibrate  only  in  the  definite  vibration  plane, 
determined  by  the  position  of  the  shorter  diagonals  of  the 


8  FUNDAMENTAL  PRINCIPLES 

end  faces  of  the  prism,  and  are  not,  like  ordinary  light, 
continually  changing  their  vibration  planes.  It  is  this 
characteristic  of  the  light  which  distinguishes  it,  in  the 
interpretation  of  the  theory,  as  "  plane  polarized." 

In  the  combination  of  the  two  Nicols  as  described,  the 
plane  polarized  beam  emerging  from  the  first  Nicol,  having 
one  resultant  vibration  plane,  passes  into  the  second  Nicol, 
where  it  is  in  general  resolved  into  two  plane  polarized 
beams,  one  of  which  is  reflected  out.  The  amount  (inten- 
sity) of  light  which  will  pass  through  the  second  prism  can 
be  determined  when  the  angle  which  its  vibration  plane 
makes  with  that  of  the  first  prism  is  known,  by  making  a 
diagram  of  the  positions  of  the  vibration  planes  of  the 
emerging  beams  of  the  two  Nicols  as  follows  : 

Let  AB  represent  the  vibration  plane  of  the  light  emerg- 
ing  from  the  first  Nicol  (which  is  known  as 
_  the  "  Polarizer  ")>  and  AD  that  of  the  emerg- 

*~  S*      "       ing  beam  from  the  Nicol  nearest  the  eye  (the 
FIG.  3. 

"analyzer"),   this   latter   plane   making   the 

angle  a  with  the  plane  of  the  polarizer. 

The  beam  defined  by  AB  is  divided,  on  entering  the 
second  Nicol,  into  two  components  whose  vibration  planes 
are  AD  and  AC,  of  which  only  the  beam  defined  by  AD 
can  emerge  from  the  analyzer.  Its  intensity  as  compared 
with  the  light  passing  through  the  polarizer  is  represented 

AD 
by  -—  ,  the  relative  lengths  of  AD  and  AB  being  deter- 


mined  by  completing  the  parallelogram  ACBD. 

When  the  Nicols  are  crossed  (that  is,  when  AB  is  per- 
pendicular to  AD\  it  will  be  seen  that  the  light  emerging 
from  the  polarizer  is  passing  along  a  vibration  plane  in 


FUNDAMENTAL  PRINCIPLES  9 

such  a  position  that  the  waves  are  totally  reflected  by  the 
analyzer,  and  the  field  is  black,  or,  in  actual  experiment, 
of  minimum  intensity,  since  usually  not  quite  all  the  rays 
entering  the  prisms  are  parallel. 

It  is  true  that  this  assumption  of  light  waves  is  purely  a 
theoretical  one.  It  is  equally  true  that  scientists  guided 
by  these  ideas  have  made  actual  laboratory  measurement? 
which  logically  seem  to  represent  light-wave  measurements. 
Reference  will  be  made  to  some  of  these  values,  which  are 
actualities  of  physics,  whatever  their  interpretation. 

Effect  of  Sugar  Solutions  on  Polarized  Light.  — (i)  If  the 
light  passing  through  a  polariscope  is  of  one  wave  length, 
that  is,  "homogeneous"  or  " monochromatic,"  as  is,  prac- 
tically, the  yellow  light  made  by  vaporizing  table  salt  in  a 
Bunsen  burner,  and  a  tube  filled  with  sugar  solution  is  placed 
between  the  two  Nicols,  so  that  the  light  passing  from  one 
prism  to  the  other  has  to  traverse  the  length  of  the  tube 
through  the  solution,  the  following  results  will  appear : 
if  the  Nicols  are  crossed,  total  extinction  does  not  now 
occur,  but  the  extinction  point  now  will  be  found  by  rotating 
the  analyzer  to  the  right  (in  the  direction  of  the  motion  of 
the  hands  of  a  clock). 

(2)  If  the  light  is  ordinary  daylight  or  lamplight,  that 
is,  white  light,  made  up  of  light  of  all  wave  lengths  ("  com- 
pound light"),  it  will  be  seen  that  extinction  does  not  take 
place  at  any  position  of  the  analyzer,  but  the  field  of  view- 
is  colored,  all  the  spectral  colors  appearing  as  the  analyzei 
is  rotated. 

The  explanation  of  these  light  effects  is  that  the  planes 
of  vibration  of  the  light  waves  of  different  lengths  are 
rotated  to  the  right  by  the  sugar  solution,  but  not  all  to 


10  FUNDAMENTAL   PRINCIPLES 

the  same  extent ;  those  of  the  shortest  length,  namely  the 
violet,  being  turned  the  most,  the  red  the  least. 

At  each  position  of  the  rotating  Nicol  the  planes  of 
vibration  of  some  of  the  rays,  those  of  some  definite  tint 
(wave  length),  make  an  angle  of  90°  with  the  principal 
section  of  the  analyzer,  and  are  consequently  reflected  and 
absorbed.  The  light  emerging  from  the  analyzer  is,  there- 
fore, the  original  light  deprived  of  the  color  of  these  reflected 
rays,  or  "  complementary  "  to  them.  In  the  case  where  the 
light  is  monochromatic,  as  is,  practically,  the  sodium  flame, 
total  extinction  occurs  when  the  rotating  Nicol  is  turned  so 
that  its  vibration  plane  is  at  right  angles  to  the  rotated 
plane  of  vibration  of  the  beam  passing  into  it  from  the 
sugar  solution.  But  one  such  plane  exists,  as  all  the  rays 
having  a  common  wave  length  are  rotated  alike. 

It  follows  that  if  the  rotatory  effect  of  a  sugar  solution 
on  plane  polarized  light  is  to  be  measured,  it  is  necessary 
to  use  monochromatic  light. 

This  behavior  of  the  sugar  solution  is  called  its  "  optical 
activity."  Any  optically  active  substance  in  solution  will 
affect  plane  polarized  light  in  a  similar  way,  rotating  the 
planes  of  vibration  to  the  right  in  some  cases,  to  the  left  in 
others.  Substances  rotating  to  the  right  are  known  as 
"  dextrorotatory  "  (symbolized  +);  those  to  the  left,  "levo- 
rotatory"  (  — ). 

Laws  governing  Rotation  of  Optically  Active  Substances. 
—  In  the  experiment  just  described,  when  the  light  is 
monochromatic,  the  angle  of  rotation  of  the  vibration  plane 
of  the  plane  polarized  light  by  a  sugar  solution  can  be 
measured  by  the  angle  through  which  the  analyzer  of  the 
polariscope  must  be  turned  to  restore  the  original  light 


FUNDAMENTAL  PRINCIPLES  II 

effect  given  by  the  instrument  previous  to  placing  the 
sugar  solution  between  the  prisms  (in  the  case  described, 
total  extinction).  This  can  be  demonstrated  by  means  of 
a  diagram  analogous  to  Fig.  3. 

The  stronger  the  sugar  solution  and  the  longer  the 
column  through  which  the  light  passes,  the  greater  the 
angle  through  which  the  vibration  plane  is  turned.  Ex- 
periment has  shown  that,  for  rays  of  any  one  wave  length, 
this  rotation  is  directly  proportional  to  the  concentration  and 
length  of  column  of  the  solution. 

Specific  Rotatory  Power.  —  When  the  angles  of  rotation 
of  different  optically  active  substances  are  compared  under 
identical  conditions  of  concentration,  column  length,  and 
light,  each  substance  gives  a  characteristic  value.  When 
determined  under  standard  conditions,  the  characteristic 
angle  obtained  is  a  measure  of  the  "  specific  rotatory  power  " 
or  "  specific  rotation  "  of  the  substance,  and  is  symbolized 
by  the  Greek  letter  alpha  (a).  In  modern  measurements, 
the  specific  rotation  of  solutions  of  optically  active  sub- 
stances is  measured  by  the  angle  of  rotation,  expressed  in 
angular  degrees,  which  plane  polarized  light,  corresponding 
in  wave  length  to  that  of  the  yellow,  D,  line  of  the  solar 
spectrum}  undergoes  in  passing  through,  at  a  temperature 

1  As  there  are  two  lines  given  by  sodium  light,  D\  and  Z>2  (the  latter  much 
brighter),  in  the  most  exact  measurements  the  ray  midway  between  the  two 
spectrum  lines  is  taken  as  the  standard,  having  a  wave  length  of  .00058932 
millimeter.  Such  light,  according  to  Landolt,  is  produced  from  a  sodium 
chloride  flame  after  passing  the  rays  successively  through  solutions  of  potas- 
sium bichromate  and  uranium  sulphate. 

The  light  of  the  D  lines  of  the  solar  spectrum  separated  by  spectroscopic 
methods  has  a  resultant  wave  length  or  "  optical  centre  "  of  .00038925  milli- 
meter and  gives  rotation  values  identical  within  the  usual  limit  of  the  measure- 
ments with  those  taken  by  the  Lippich  filtered  sodium  light. 


12  FUNDAMENTAL  PRINCIPLES 

of  20°  C.y  a  decimeter  column  of  a  solution  of  the  optically 
active  substance  having  a  concentration  of  one  gram  in  one 
cubic  centimeter.  This  can  be  expressed  by  the  following 
equation:  a==a^  (l) 

where  a  is  the  angle  of  rotation  in  degrees,  I  the  length  of 
column  in  decimeters,  and  c  the  concentration.  If  there 
are  w  grams  of  substance  in  v  cubic  centimeters  of  solution, 

the  concentration  can  be  expressed  as  ~ 

v 


Hence,  a  =        ,  (2) 

V 

and  ._£.  (3) 

By  this  last  equation,  the  specific  rotatory  power  of  any 
optically  active  substance  can  be  calculated  from  solutions 
of  any  convenient  concentration  if  the  column  length  is 
known.  As  will  be  seen  later,  effects  so  obtained  in  many 
cases  have  to  be  corrected  for  influence  of  solvent  and  tem- 
perature, but  for  cane  sugar  these  effects  are  practically 
negligible  for  ordinary  conditions  of  analysis.  These  spe- 
cific rotation  values  are  the  fundamental  constants  of  all 
calculations  in  optical  analysis,  being  analogous  in  their 
use  to  the  atomic  weights  in  the  usual  computations  of 
gravimetric  and  volumetric  analysis. 

If  the  concentration  of  a  solution  is  expressed  in  per- 
centage of  substance  in  solution  (grams  in  100  grams),  as 
is  often  the  case  in  commercial  analysis,  equations  (2)  and 
(3)  are  expressed  somewhat  differently.  The  number  of 
grams  in  100  grams  can  be  expressed  as  /,  and  since,  if  d 

represents  the  density  of  the  solution,  v  =  ^—  -,  .*.  —  =  —  — 

d          v      100 


FUNDAMENTAL  PRINCIPLES  13 

Hence,  ^ 


—'fir  (5> 

Obviously  it  is  necessary  to  distinguish  carefully  be 
tween  these  two  expressions  of  concentration,  in  order  to 
avoid  serious  confusion  in  calculations.1 

Yellow  light,  corresponding  to  the  D  line  of  the  solar 
spectrum,  has  been  adopted  for  the  standard  because  of 
the  ease  with  which  light  of  this  color  can  be  produced  by 
volatilizing  table  salt  in  a  Bunsen  burner,  alcohol  lamp,  or 
other  source  of  hot  non-luminous  flame.  Specific  rotations 
so  determined  are  more  exactly  symbolized  [a]/,  to  dis- 
tinguish them  from  others  to  be  referred  to. 

In  the  case  of  an  optically  active  substance  which  is 
itself  a  liquid,  as,  for  instance,  spirits  of  turpentine,  the 
specific  rotatory  power  is  expressed  by  the  equation 

-ar 

where  d  is  the  density  of  the  liquid. 

In  the  case  of  an  optically  active  transparent  solid,  as 

quartz,  a  =  -,  the  unit  for  /  being  a  section  one  millimeter 

/ 

thick  cut  in  a  plane  at  right  angles  to  the  optic  axis.     The 
standard  temperature  for  all  specific  rotations  is  20°  C. 

1  In  very  accurate  determinations  of  specific  rotation  the  concentration  is 
expressed  in  percentage  of  substance  in  solution,  both  substance  and  solvent 
being  weighed  and  all  weights  being  absolute,  that  is,  calculated  for  weighings 
in  a  vacuum.  In  the  case  of  the  weight  of  a  solid  substance  of  the  density  of 
cane  sugar  the  difference  between  the  weighings  in  air  and  the  absolute  is 
only  .06%. 


14  FUNDAMENTAL   PRINCIPLES 

Application  of  the  Laws  of  Optical  Rotation  to  Sugar 
Analysis.  —  The  application  of  these  laws  to  the  analysis 
of  sugar  or  other  optically  active  substance  can  now  readily 
be  understood.  Let  P  be  the  per  cent  of  optically  active 
substance  contained  in  wr  grams  of  sample,  the  weight  of 
this  optically  active  substance  being  w. 

Then,  P=  — ,  P  being  expressed  decimally. 
From  the  fundamental  equation  already  given : 

av 

w  =  —- 
a/ 

T-U  D       av 

Then,  />=         . 

a/ze/ 

For  example,  17.50  grams  of  raw  sugar  in  water  solution, 
made  up  to  100  cubic  centimeters,  observed  in  a  2-deci- 
meter tube,  rotated  the  plane  polarized  yellow  ray  21°  35'. 
Taking  the  specific  rotation  of  cane  sugar  as  66.5°  and 
expressing  all  values  in  standard  units,  the  percentage  of 
cane  sugar  can  be  expressed  as  follows : 

2158X100.      =  !   (Aat  .      92.7%). 

2X66.5X17.50 

If  the  substance  has  its  rotation  constant  appreciably 
affected  by  the  amount  of  solvent  present,  as  is  the  case 
with  camphor  or  tartaric  acid,  the  calculation  will  be  more 
complicated.  Under  the  ordinary  conditions  of  commer- 
cial sugar  analysis,  this  influence  is  so  small  as  to  be  negli- 
gible, as  already  stated. 

1  Throughout  this  discussion  it  is,  of  course,  assumed  that  but  one  optically 
active  substance  is  present  in  solution. 


THE   POLARISCOPE 

Essential  Parts.  —  From  the  preceding  chapter  it  is 
clear  that  the  essential  parts  of  a  polariscope  for  meas- 
uring the  rotatory  effects  of  optically  active  substances  are 
two  Nicol  prisms,  one  of  which  must  be  capable  of  rota- 
tion and  have  some  suitable  device  for  measuring  the  angle 
of  its  rotation  from  a  definite  position.  These  prisms 
must  be  arranged,  as  previously  described,  in  a  suitable 
holder,  so  that  tubes  containing  solutions  to  be  examined 
can  be  placed  between  the  prisms,  and  finally  there  must 
be  some  source  of  monochromatic  light. 

As  a  rule  the  analyzer  is  the  rotating  prism,  as  this 
brings  the  measuring  scale  conveniently  near  the  eye  of 
the  observer. 

In  1840  Biot  introduced  a  polariscope  of  this  descrip- 
tion, using  the  total  extinction  position  of  the  prisms  for 
the  end  point ;  but,  as  experiment  with  such  an  instrument 
will  show,  it  was  impossible  to  determine  the  exact  point 
of  extinction  without  a  large  error.  In  the  optical  devices 
for  producing  a  more  precise  end  point,  much  ingenuity 
has  been  expended ;  in  fact,  these  devices  alone  determine 
the  essential  differences  between  most  of  the  different 
makes  of  polariscopes  for  measuring  angles  of  rotation 
directly. 

Mitscherlich  Polariscope.  —  Mitscherlich,  in  1844,  im- 
proved the  original  instrument  of  Biot,  so  that  a  broad 

'5 


i6 


THE   POLARISCOPE 


black  band  in  a  light 
field  was  produced  at  the 
extinction  point,  instead 
of  total  darkness.  The 
Mitscherlich  polariscope 
is  still  used  for  compar- 
atively rough  measure- 
ments, being  sensitive 
to  .1°. 

The  Transition-tint 
Polariscope.  —  Another 
end-point  device,  used 
in  the  earlier  instruments 
,by  Biot  arid  others, 
was  the  "transition-tint" 
quartz  plate.  Sections 
of  quartz,  cut  perpen- 
dicular to  the  optic  axis 
of  the  crystal,  have  a 
strong  rotatory  effect 
on  plane  polarized  light 
when  the  light  passes 
parallel  to  the  optic  axis, 
some  crystals  turning 
the  plane  of  polarization 
to  the  right  (clockwise), 
others  to  the  left.  The 
direction  in  which  the 
planes  of  vibration  ro- 
tate can  be  predicted  by 
a  study  of  the  arrange- 


THE   POLARISCOPE  .  17 

ment  of  the  faces  of  the  original  crystal.  The  amount  of 
rotation  is  independent  of  the  right  or  left  .direction,  but 
depends  on  the  thickness  of  the  quartz  section.  A  milli- 
meter section  of  quartz,  according  to  Biot,  rotates  plane 
polarized  light  of  different  colors  about  as  follows : 

Red,  19*      Yellow,  24°       Green,  28°       Violet,  41° 

These  values  are  for  "mean"  rays,  or  those  approxi- 
mately in  the  middle  of  the  spectrum  bands  of  the  colors 
mentioned,  and  do  not  apply  to  the  "  Fraunhofer '"  lines  as 
do  the  more  exact  measurements  of  later  observers.  1 

The  transition-tint  plate  consists  of  two  quartz  sections, 
cut  ^s  described,  of  equal  thickness,  but  of  opposite  rota- 
tions. These  are  mounted  in  a  diaphragm  opening  be- 
tween the  polarizer  and  analyzer,  in  such  a  way  that  each 
,  section  covers  half  of  the  optical  field  of  the  polariscope. 
The  sections  are  cut  3.75  millimeters  thick,  and  rotate  the 
mean  yellow  rays  90°  (3.75  X  24  =  90),  which  in  conse- 
quence cannot  pass  through  the  analyzer  when  its  plane 
of  polarization  is  parallel l  to  that  of  the  polarizer.  White, 
or  any  light  containing  rays  of  all  wave  lengths,  as  lamp 
or  gas  light,  in  passing  through  such  an  optical  combina- 
tion will  be  deprived  of  its  yellow  rays,  and  the  optical 
field  will  show,  accordingly,  the  resulting  "complement- 
ary" tint,  usually  described  as  a  rose  violet.  If  the 
analyzer  is  turned  in  the  least,  contrasting  tints  of  red  and 
blue  are  seen  in  opposite  halves  of  the  field.  Only  at  the 
end  point,  or  at  a  position  of  the  analyzer  180°  from  it,  do 

1  A  section  cut  any  odd  multiple  of  3.75  millimeters  in  thickness  will  pro- 
duct the  same  effect.     When  the  plate  is  cut  an  even  multiple,  it  is  easily 
demonstrated  that  the  transition  tint  appears  when  the  Nicols  are  crossed. 
c 


1 8  THE   POLARISCOPE 

both  halves  of  the  field  show  the  same  tint,  —  this  rose- 
violet  transition  tint. 

The  transition-tint  polariscope  was  introduced  by  Robi- 
quet,  and  was  much  used  by  earlier  investigators,  as  it  was 
more  sensitive  than  the  Mitscherlich,  and  had  the  advan- 
tage of  using  ordinary  light. 

Inasmuch  as  this  instrument  gave  measurements  of  the 
rotation  of  the  vibration  plane  of  the  mean  yellow  ray, 
and  not  that  of  the  D  line  of  the  sodium  flame,  it  gave  rise 
to  statements  of  rotation  figures  on  a  different  standard, 
which  is  distinguished  by  the  symbol  [a];-,  the  mean  yel- 
low ray  of  wave  length  .0005608  millimeter,  being  known 
as  the/ ray  (French  jaune,  yellow). 

The  transition-tint  polariscope  is  not  now  used  in  scien- 
tific measurements,  although  the  transition-tint  plate  is  the 
end-point  device  of  some  modern  saccharimeters.  The 
instrument  has  many  disadvantages.  Colored  solutions 
obviously  interfere  with  its  readings.  Many  colorless  solu- 
tions of  high  rotation  produce  dispersive  disturbances 
which  prevent  an  even-tinted  field  at  the  end  point.  It 
has  been  objected  to  on  the  ground  that  lights  of  different 
wave-length  composition,  such  as  daylight  and  gaslight,  give 
slightly  different  complementary  tints.  The  instrument  is 
of  course  useless  to  those  who  are  color-blind.  A  cheap 
form  of  this  polariscope  is  used  in  Europe  somewhat  for 
determining  sugar  in  wines,  as  the  errors  of  such  low 
rotations  are  inconsiderable. 

The  transition-tint  polariscope  —  which  must  not  be  con- 
founded with  the  Soleil  saccharimeter  —  is  of  importance 
to  the  modern  investigator  solely  because  the  optical  con- 
stants which  were  obtained  by  its  measurements  are  still 


THE   POLARISCOPE  19 

found  in  many  modern  works,  especially  English,  and  con- 
sequently the  difference  between  specific  rotatory  powers 
expressed  by  [a]/>  and  [a]^  should  be  understood.  Inas- 
much as  the  rotation  for  the  D  line  of  the  spectrum  by  a 
millimeter  section  of  quartz  is  21.7°,  that  of  the  mean  yel- 
low being  24°,  as  previously  stated,  the  old  transition-tint 
constants  can  be  changed  to  the  modern  standard  by  the 

factor,  iii^.i 
24.0 

Practically  all  modern  polariscopes  use  the  sodium  light, 
and  have  some  device  which  shows  a  blank,  evenly 
illuminated  field  at  the  end  point,  while  at  any  other  posi- 
tion of  the  analyzer,-  a  part  of  the  field,  usually  one  half,  is 
shaded.  One  of  the  earliest  of  these  "  shadow  "  or  "  half- 
shade  "  polariscopes  was  devised  by  Jellet  about  1860. 
Cornu  and  Duboscq  improved  the  instrument  in  some 
details  of  its  construction. 

The  Duboscq  Half -shade  Rotatometer.  —  The  end-point 
device  of  the  Duboscq  half-shade  "rotatometer,"  as  it  is 
called,  is  the  Jellet-Cornu  or  "  split "  prism,  which  takes  the 
place  of  the  ordinary  polarizer.  This  is  made  by  bisecting 
a  Nicol  prism,  or  one  of  its  sections,  lengthwise  of  the 

1  Some  confusion  has  resulted  from  the  introduction  by  Montgolfier  in  1874 
of  a  jaune  moyen  ray,  having  a  rotation  value  of  24.5°  for  the  quartz  milli- 
meter plate,  subsequently  adopted  by  Landolt  in  his  book  on  the  polariscope 
as  the  value  for  the  j  measurements.  This  ray  is  not  the  Biot  ray,  inter- 
mediate in  wave-length  value  between  the  sodium  and  thallium  lines  of  the 
solar  spectrum  and  having  a  wave  length  of  .0005608  millimeter,  but  is  the 
ray  of  a  wave  length  .0005553  of  a  rotation  value  for  the  quartz  millimeter 
plate  which  is  the  arithmetical  mean  between  the  rotation  values  for  the  D  ray 
and  the  E  ray.  This  later  change  of  standard  was  most  unfortunate,  as  it  has 
caused  a  misunderstanding  which  has  marred  much  excellent  work  by  early 
investigators  [/.  Chem.  Soc.,  1897  (71),  89]. 


20  THE   POLARISCOPE 

prism,  in  the  plane  passing  through  the  shorter  diagonals  of 
the  end  faces.  Equal  wedge-shaped  sections  are  taken  off 
the  two  cut  surfaces,  and  the  two  parts  are  cemented  to- 
gether again.  The  effect  of  the  removal  of  the  two  wedge- 
shaped  sections  is  to  tilt  the  polarizing  planes  of  the  two 
halves  of  the  prism  so  that  they  make  an  angle  (usually 
about  1/5°)  with  each  other.  This  type  of  prism  is  made 
in  several  ways,  but  the  principle  is  the  same  in  every  form. 
This  modified  prism  is  used  as  a  polarizer,  and  is  mounted 
in  the  polariscope  with  a  diaphragm  having  a  circular  open- 
ing between  it  and  the  analyzer  in  such  a  way  that  the 
opening  is  bisected  vertically  by  the  line  of  the  joint  of  the 
two  halves  of  the  prism.  If  the  analyser  is  turned  to  a 
position  which  would  give  total  extinction  for  an  instrument 
fitted  with  an  ordinary  Nicol  for  a  polarizer,  the  field  made 
by  the  diaphragm  opening  will  not  be  black  in  this  case, 
\>\&  faintly  and  evenly  illuminated,  appearing  as  a  luminous 
disk.  The  slightest  rotation  of  the  analyzer  from  this  posi- 
tion produces  a  shading  in  one  or  the  other  halves  of  the 
field.  This  can  be  made  clear  by  a  discussion  of  the  follow- 
ing diagram : 


Let  AC  and  FG  respectively  represent  the  positions  of 
the  planes  of  polarization  of  the  analyzer  and  polarizer  of 
a  polariscope  equipped  with  ordinary  Nicol  prisms  adjusted 


THE   POLARISCOPE  21 

for  total  extinction,  A  C  being  at  right  angles  to  FG.  If  a 
Jellet-Cornu  prism  is  substituted  for  the  Nicol  prism  polar- 
izer, but  placed  in  the  same  relative  position  as  the  latter, 
the  plane  of  polarization  of  the  polarizer  will  no  longer  be 
represented  by  the  line  FG,  but  can  be  by  the  broken  line 
DEEB,  if  DE  and  EB  represent  the  respective  positions  of 
he  planes  of  each  half  of  the  prism.  In  the  position  of 
Jie  polarizer  assumed,  these  planes  make  equal  angles, 
DEA  and  BE  A,  with  the  plane  of  the  analyzer  AC. 

Consequently,  as  these  angles  are  also  less  than  a  right 
angle,  the  optical  field  defined  by  the  circle  which  repre- 
sents the  diaphragm  opening  will  appear  evenly  but  faintly 
illumined. 

If  the  analyzer  is  rotated,  its  plane  of  polarization  AC  will 
approach  a  right  angle  with  one  of  the  polarizing  planes 
DE  or  EB,  and  a  shadow  will  appear  in  the  corresponding 
half  of  the  field.  Thus  there  is  only  one  position  of  the 
analyzer,  within  180°,  where  both  halves  of  the  field  appear 
evenly  illuminated,  and  from  which  position  the  slightest 
rotation  of  the  analyzer  gives  a  shadow  in  one  half  of  the 
field  or  the  other.  This  is  the  true  end  point.  It  is 
true  that  the  intermediate  positions  at  90°  give  a  (bright) 
evenly  illumined  field,  but  no  shadows  appear  on  slightly 
rotating  the  analyzer,  as  is  evident  from  a  study  of  the 
diagram. 

The  Duboscq  rotatometer  is  an  accurate  and  sensitive 
instrument,  and  can  be  used  with  any  kind  of  homogeneous 
light.  Formerly  it  was  much  used  in  France.  The  diagram 
also  shows  that,  the  nearer  the  angle  of  the  tilting  of  the 
planes  of  polarization  of  the  two  halves  of  the  prism  to 
1 80°,  the  more  sensitive  is  the  polariscope  to  small  angles 


22  THE  POLARISCOPE 

of  rotation ;  but,  on  the  other  hand,  the  field  is  darker  at 
the  end  point.  This  indicates  the  most  serious  disadvantage 
of  this  type  of  polariscope,  as  it  is  impossible  to  make  one 
instrument  that  will  be  applicable  for  universal  laboratory 
measurements.  If  the  polariscope  has  a  prism  giving  suf- 
ficient precision  for  scientific  work,  it  will  not  pass  light 
enough  at  the  end  point  for  polarizing  the  dark-colored  solu- 
tions often  met  with  in  commercial  practice,  molasses  for 
instance. 

Laurent  Polariscope.  —  This  need  for  a  half-shade  polari- 
scope, having  an  end-point  device  by  which  the  angle  of 
the  polarizing  planes  of  the  two  halves  of  the  field  could 
be  varied  to  suit  the  requirements  of  the  work,  was  met  in 
a  most  ingenious  and  satisfactory  manner  by  Laurent  in 
1877. 

The  Laurent  polariscope  has  the  ordinary  Nicol  prisms 
for  polarizer  and  analyzer,  mounted  in  the  usual  way,  except 
that  the  polarizer  is  so  arranged  that  it  can  be  rocked  or 
rotated  on  its  long  axis  through  a  small  angle.  The  char- 
acteristic end-point  device  is  a  thin  plate  of  quartz  cut  par- 
allel to  the  optic  axis  of  the  crystal.  A  section  so  cut  is 
doubly  refractive,  dividing  a  light  beam  entering  normal  to 
its  surface  into  two  component  beams  with  vibration  planes 
respectively  perpendicular  and  parallel  to  the  optic  axis. 
The  thickness  of  the  section  is  such  that,  when  sodium 
light  is  used,  the  component  ray  vibrating  at  right  angles 
to  the  optic  axis,  on  emerging,  has  its  vibrations  accelerated1 
half  a  wave  length  in  its  passage  through  the  quartz.  This 

1  The  undulatory  theory  shows  that  the  difference  in  refraction  of  the  two 
polarized  rays  is  the  result  of  a  difference  in  speed  of  transmission  of  the  light 
waves,  the  less  refracted  ray  being  transmitted  more  rapidly. 


THE   POLARISCOPE 


quartz  plate  covers  one  half  of  the  circular  opening  of  a 
diaphragm  which  defines  the  optical  field  of  the  instru- 
ment, and  through  which  the  light  passes  from  polarizer 
to  analyzer.  Therefore  the  quartz  intercepts  these  rays  in 
one  half  of  the  field. 

The  following  diagram  will  assist  the  explanation :  Let 
AB  represent  the  vibration  plane  as  well  as  the  amplitude 
of  vibration  of  the  light  from  the  polarizer  which  makes  a 
small  angle  BA  C  with  the  s 

optic  axis  of  the  quartz 
plate,  this  axis  being  repre- 
sented for  convenience  as 
parallel  to  the  edge  AC  of 
the  quartz  plate  bisecting 
the  circle  representing  the 
diaphragm  opening.  When 
the  light  from  the  polarizer 
reaches  the  quartz,  it  is 
resolved  into  two  compo- 
nents A  C  and  AF,  parallel 
and  perpendicular  to  the 
optic  axis.  The  light  of  the  component  AF  travels  faster 
through  the  quartz  than  that  of  the  component  A  C  vibra- 
ting parallel  to  the  axis,  and,  having  gained  on  AC  half 
a  wave  length,  is  at  time  of  emergence  from  the  quartz  in 
just  the  opposite  phase  of  vibration,  relative  to  AC,  to  its 
original  phase  on  entering  the  quartz.  Consequently,  this 
emerging  component  can  be  represented  by  the  line  AE 
equal  to  AF,  but  opposite  in  direction.  By  means  of  the 
parallelogram  AEGC  it  can  be  shown  that  the  components 
AE  and  AC  can  be  compounded  into  the  resultant  AG,  as 


FIG.  6. 


24  THE   POLARISCOPE 

if  the  light  had  come  from  a  polarizer  having  its  vibration 
plane  inclined  to  the  optic  axis  of  the  quartz  at  an  angle 
GAC  equal  and  symmetrical  to  the  angle  BAG  actually 
made  by  the  plane  of  the  polarizer  with  the  optic  axis.  So 
too  the  angles  made  by  these  planes  with  that  of  the  ana 
lyzer  are  equal  and  symmetrical,  when  it  is  adjusted  sc 
that  its  vibration  plane  is  perpendicular  to  the  optic  axis  of 
the  quartz,  and  hence  the  intensity  of  the  light  in  both 
halves  of  the  field  is  the  same,  the  absorption  and  reflec- 
tion caused  by  the  quartz  being  negligible.  Thus,  the 
polarizer  and  the  quartz  plate  together  give  the  effect  of  a 
Jellet-Cornu  prism,  the  planes  of  which  are  tilted  to  each 
other  in  each  half  of  the  field  by  a  small  angle  ;  but  have  the 
valuable  advantage  that  this  angle  can  be  varied  at  will  by 
means  of  the  rocking  polarizer  without  disturbing  the  end- 
point  adjustment  of  the  analyzer,  since  the  angles  made  by 
the  vibration  planes  of  the  light  in  each  half  of  the  field  with 
the  analyzer  plane  always  remain  equal  and  symmetrical 
whatever  their  magnitude.  In  all  other  respects,  the  ex- 
planation of  the  light  effects  of  the  Jellet-Cornu  prism 
polariscope  applies  to  the  Laurent  instrument,  so  need  not 
be  enlarged  upon  here. 

The  Laurent  polariscope  is  the  one  most  generally  used 
in  direct  laboratory  measurements  of  optical  rotation,  and 
is  the  standard  instrument  used  by  the  French  govern 
ment  in  testing  sugars.  Its  use  is  obviously  restricted  to 
sodium  light.  The  average  error  of  measurement  is  stated 
by  Landolt  to  be  .2  per  cent,  due  to  mechanical  imperfec- 
tions inseparable  from  its  construction.  First-class  French 
instruments  certainly  show  agreement  within  an  error  con- 
siderably less  than  .2  per  cent. 


THE   POLARISCOPE  2$ 

Lippich  Polariscope.  —  The  Lippich  polariscope,  which  is 
specially  made  for  most  precise  measurements  of  optical 
rotation,  uses  a  small  Nicol  for  its  shadow  device,  which  is 
placed  between  the  polarizer  and  the  analyzer,  close  to  the 
former,  and  covers  half  of  the  field,  being  mounted  in  an 
analogous  manner  to  the  Laurent  quartz  plate.  The  po- 
larizer is  mounted  so  that  its  plane  of  polarization  makes 
a  slight  angle  with  that  of  the  small  Nicol,  which  latter  is 
known  as  the  "half  prism."  This  angle  can  be  varied  at 
will  by  a  device  which  permits  the  polarizer  to  be  moved 
axially,  an  index  showing  the  exact  position  of  its  plane  of 
polarization  relative  to  that  of  the  half  prism. 

This  instrument  is  said  to  be  free  from  the  errors  believed 
to  be  inherent  in  the  construction  of  the  Laurent  polari- 
scope, and  can  be  used  to  measure  rotations  of  homo- 
geneous light  of  any  wave  length.  It  has  the  disadvantage 
that  the  angle  of  the  shadow  device  cannot  be  changed 
without  altering  the  end-point  adjustment  of  the  analyzer. 
The  Lippich  polariscope  is  often  constructed  with  great 
elaboration  and  nicety  of  adjustment,  and  is  capable  of 
measurements  to  .001°  with  a  mean  error,  according  to 
Landolt,  of  i$u  or  about  .004°.  By  means  of  a  double 
prism  end-point  device,  the  field  can  be  divided  into  three 
parts.  It  is  estimated  that  the  eye  can  distinguish  the 
shadow  change  in  a  triple-field  instrument  with  twice  the 
precision,  or  to  8".  These  very  precise  instruments  are 
used  only  in  the  most  exact  physical  measurements.1 
In  ordinary  laboratory  work  polariscopes  are  used  which 

1  For  complete  descriptions  of  these  polariscopes,  see  Landolt's  "  Das  op- 
tische  Drehungsvermogen."  See  also  my  remarks  on  triple-shade  saccha- 
rimeters. 


26  THE   POLARISCOPE 

measure  to  i',  or,  with  the  more  modern  decimal  scale, 
.01°. 

In  using  the  Lippich  polariscope  it  is  necessary  that  the 
condensing  lenses  for  illuminating  the  field  be  adjusted 
with  the  greatest  care  to  insure  even  illumination  without 
surface  reflections.  The  instrument  also  seems  to  be 
much  more  sensitive  to  extraneous  light  than  is  the  Lau- 
rent polariscope. 

Wild  Polariscope  (?Polaristrobometer"\  —  The  Wild  po- 
laristrobometer,  invented  in  1864,  has  for  its  end-point 
device  a  "  Savart  polariscope,"  which  consists  of  two  calc- 
spar  plates  cut  at  45°  to  the  optical  axis  of  the  crystal  and 
placed  with  their  vibration  planes  at  right  angles  to  each 
other1  and  at  45°  to  that  of  the  analyzer,  which  is  fixed, 
the  polarizer  being  the  rotating  prism.  The  effect  of  this 
combination  is  to  produce  "  interference  bands"  or  black 
horizontal  stripes  in  the  field  when  homogeneous  light  is 
used.  These  bands  disappear  in  the  centre  of  the  field  at 
points  90°  apart  in  the  rotation  of  the  polarizer.  The 
exact  point  of  disappearance  of  these  bands,  as  shown  by  a 
blank  space  symmetrically  placed  relative  to  two  cross 
hairs  in  the  field,  is  taken  as  the  end  point.  The  displace- 
ment of  this  blank  spot  in  the  field  is  very  marked  for  a 
slight  rotation  of  the  polarizer. 

As  it  is  the  polarizer  that  rotates,  its  rotation  is  in  the 
reverse  sense  to  the  rotation  of  the  plane  of  polariza- 
tion by  the  optically  active  substance ;  that  is,  dextrorota- 
tory substances,  for  instance,  have  their  rotatory  effects 
measured  by  a  corresponding  rotation  of  the  polarizer  to 
the  left. 

1  Wild,  "Ueber  ein  neues  Polaristrobometer,"  Berne,  1865. 


THE   POLARISCOPE  27 

The  Wild  instrument  has  not  been  popular  in  the 
United  States,  owing  to  the  unusual  end  point  and  the 
awkwardness  of  manipulation.  It  is,  however,  for  a  prac- 
ticed observer,  sensitive  and  precise  enough  for  most  labo- 
ratory measurements. 


THE   SACCHARI METER 

General  Principles.  —  As  the  value  of  the  polariscope  for 
the  determination  of  sugar  (sucrose)  had  quick  recognition 
in  commercial  work,  instruments  were  soon  specially  de- 
signed to  give  the  sugar  content  of  industrial  products  by 
a  simpler,  more  direct  way  than  by  the  use  of  the  ordi- 
nary laboratory  polariscope.  Such  instruments,  known 
as  "  saccharimeters,"  have  scales  graduated  in  divisions 
expressing  per  cents  of  sugar  instead  of  angular  degrees, 
and  the  manipulation  of  testing  is  so  conducted  that  the 
saccharimeter  gives  a  direct  reading  of  the  sugar  per  cent 
of  the  sample  without  calculation. 

The  theory  of  the  graduation  of  a  saccharimeter  is  very 
simple.  As  the  optical  rotation  is  directly  proportional  to 
the  concentration  of  the  optically  active  solution  and  the 
tube-length,  it  is  clear  that  if  the  weight  of  sugar  sample 
taken  for  polarization,  the  volume  of  aqueous  solution  in 
which  this  weight  of  sample  is  dissolved,  and  the  tube-length 
are  constants,  the  sole  variable  effect  on  the  rotation  (leav- 
ing out  of  consideration  the  slight  influence  of  temperature 
and  concentration  on  the  specific  rotation)  will  be  caused 
by  the  difference  in  the  amount  of  sugar  in  the  sample. 
Further,  if  the  constant  weight  of  sample  taken  for  polari- 
zation is  that  weight  of  pure  sugar  which  will  give  a  read- 
ing of  100  divisions  of  the  saccharimeter  scale,  the  reading 

•  28 


THE   SACCHARIMETER  29 

when  this  weight  of  any  sample  of  sugar  is  polarized  will 
directly  express  the  per  cent  of  sugar  in  the  sample.  This 
weight  is  known  as  the  "  normal  weight"  of  the  saccha- 
rimeter. 

It  is  necessarily  assumed  that  no  other  optically  active 
substance  than  sugar  (sucrose)  is  present  in  the  sample. 

The  most  convenient  values  for  tube-length  and  volume, 
universally  adopted  in  saccharimetry,  are  2  decimeters  and 
100  cubic  centimeters.  The  standard  commercial  saccha- 
rimeter  in  this  country  and  abroad,  except  in  France,  has 
a  normal  weight  of  26.048  grams. 

Originally,  a  different  standard  of  graduation  was  used, 
and  it  still  prevails  in  the  rotary  saccharimeters,  which 
were  the  earliest  type.  On  this  account  it  may  be  profit- 
able to  show  the  origin  of  these  standards  of  graduation. 
The  angular-degree  graduation  is  not  suited  for  a  saccha- 
rimeter  scale,  as  simple  calculation  will  show.  By  the 

aij 

formula,  w=—,  derived  from  the  fundamental  equation 
cu 

expressing  optical  rotation,  making  a :  100,  /:2,  ^:ioo, 
and  taking  [a]/>  of  sucrose  in  aqueous  solution  as  66.50: 

100  x  100 
w  =  — =  75.2  grams  of  sugar  as  the  normal  weight 

DO.  5X2 

for  the  angular-degree  scale.  This  is  an  impracticable 
amount  of  sugar  to  dissolve  in  100  cubic  centimeters  of 
water  at  ordinary  laboratory  temperature.  The  saccha- 
rimeter  graduation  consequently  requiring  a  smaller  rota- 
tion value  for  its  100  point,  a  convenient  constant  was 
found  in  the  specific  rotation  of  quartz,  that  is,  that  caused 
on  the  D  ray  by  a  millimeter  section  of  right-rotating  quartz 
cut  perpendicular  to  its  optic  axis.  This  value  as  originally 


3<D  THE   SACCHARIMETER 

determined  was  21.667°  at  l7-5°  C.  for  light  obtained  by 
vaporizing  sodium  chloride  in  a  Bunsen  burner  and  using 
as  a  ray  filter  a  section  of  potassium  bichromate  crystal. 
The  normal  weight  of  sugar  found  by  the  equation  given 
above  for  the  commercial  standard  of  volume  and  tube- 
length  is  16.29  grams. 

When  the  sugar  is  dissolved  in  100  " reputed"  or  Mohr 
cubic  centimeters  on  a  temperature  standard  of  17.5°  C., 
as  is  the  custom  in  commercial  work,  the  normal  weight  is 
16.32,  owing  to  the  volume  of  the  Mohr  flask  being  .23 
per  cent  greater  than  the  "  true  "  cubic  centimeter  flask.1 
This  will  be  discussed  later. 

The  Laurent  and  Duboscq  rotatory  polariscopes  are  pro- 
vided with  saccharimetric  scales  of  this  graduation,  in  addi- 
tion to  their  angular  degree  scales.  The  Wild  polariscope 

1  Much  misapprehension  prevails  as  to  the  exact  value  of  the  normal  weight 
of  the  Laurent  saccharimeter.  This  is  partly  due  to  the  existence  of  instru- 
ments standardized  for  a  normal  weight  of  16.19  grams,  and  partly  to  the  fact 
that  the  specific  rotation  of  quartz  has  been  redetermined  by  instruments  using 
light  of  a  different  wave  length  than  that  used  for  the  ordinary  laboratory  type 
of  Laurent  polariscope. 

No  light  obtained  from  a  sodium  flame  by  the  ordinary  methods  is  "  opti- 
cally pure,"  of  one  definite  wave  length,  but  contains  light  of  many  wave 
lengths  differing  by  but  small  values  from  that  of  the  two  D  rays,  which  are 
themselves  obviously  of  two  different  wave  lengths. 

Such  light  acts  like  absolutely  homogeneous  light  of  a  wave  length  corre- 
sponding to  a  ray  which  represents  the  resultant  intensity  of  these  diverse  rays, 
its  wave  length  being  called  by  the  Germans  the  "  Schwerpunkt"  or  "centre 
of  gravity  "  of  the  light.  The  "  optical  centre  of  gravity  "  of  the  light  used 
in  the  later  measurements  of  quartz  differed  from  that  used  in  the  Laurent 
polariscope,  and  apparently  has  given  rotations  about  .2  per  cent  larger. 

Evidently,  a  normal  weight  of  sugar  calculated  on  the  rotation  value  of 
a  millimeter  section  of  quartz  would  be  higher  also  in  the  same  ratio. 

As  a  matter  of  fact,  the  normal  weight  of  the  standard  Laurent  saccharim- 
eter has  been  a  fixed  value  for  years,  being  actually  that  weight  of  sugar 
which,  dissolved  under  standard  conditions  of  concentration  and  tube-length, 


THE   SACCHARIMETER  31 

has  an  additional  saccharimetric  scale  divided  into  400 
divisions,  100  of  which  correspond  to  10  grams  of  sugar 
dissolved  in  100  cubic  centimeters. 

Quartz-wedge  Saccharimeters.  General  Principles. — In 
commercial  work,  where  many  rapid  polarizations  have  to 
be  made,  the  sodium  light  is  inconvenient  to  maintain  and 
trying  to  the  eyesight.  At  the  same  time,  owing  to  the 
unequal  rotation  dispersion  of  the  rays  of  different  wave 
length,  it  is  impracticable  to  use  the  saccharimeter  with 
rotating  analyzer,  and  measure  the  rotation  of  the  polarized 
light  directly,  if  the  light  used  is  white  or  of  a  compound 
nature.  This  has  been  explained  in  the  chapter  on  Funda- 
mental Principles. 

The  problem  of  devising  a  saccharimeter  for  use  with 
ordinary  lamp  or  day  light  was  solved  most  ingeniously  by 
the  quartz-wedge  compensator,  invented  in  1848  by  Soleil, 
who  found  that  the  rotatory  effect  of  sugar  solutions  could 
be  exactly  neutralized  by  a  plate  of  left-rotating  quartz  of 
appropriate  thickness.  The  kind  of  light  has  no  influence, 
as,  owing  to  the  fact  that  the  dispersive  power  of  quartz 
and  sugar  in  water  solution  are  practically  the  same  (that 
is,  the  planes  of  polarized  light  of  different  wave  lengths 
are  turned  in  the  same  proportion  by  sugar  solutions  and 
quartz),  the  plane  of  polarization  of  each  ray  is  brought 

gives  a  rotation  of  21°  40'  (21.667°)  to  tne  ravs  of  a  sodium  chloride  flame 
filtered  through  a  section  of  potassium  bichromate  crystal.  Whether  this  rota- 
tion value  is  the  accepted  one  for  the  specific  rotation  of  quartz  or  not  is 
immaterial  for  accuracy  in  saccharimetry,  or  even  for  rotation  measurements, 
if,  in  the  latter  case,  the  wave-length  value  of  the  optical  centre  of  the  light  is 
known.  Apparently,  there  have  been  no  wave-length  determinations  of  the 
optical  centre  of  light  as  actually  used  by  the  Laurent  saccharimeter  in  sugar 
testing. 

The  earlier  saccharimeters  of  Duboscq  used  a  normal  weight  of  16.35  grams. 


32  THE   SACCHARIMETER 

back  to  the  same  angular  position  which  it  had  before 
being  rotated  by  the  sugar  solution.1 

Hence,  for  any  concentration  of  solution  there  is  a  cor- 
responding thickness  of  left-rotating  quartz  which  will  just 
neutralize  (compensate  for)  the  rotatory  effect  of  the  sugar. 
The  Soleil  quartz-wedge  compensator  is  a  device  for  intro- 
ducing at  will  what  is  in  effect  a  section  of  left-rotating 
quartz  of  the  desired  thickness  between  the  polarizer  and 
analyzer. 

The  diagram,  shown  as  a  plan,  will  explain  the  compen- 
sator and  its  working.     AB  represents  the  line  of  trans- 
c  mission   of   the   light   through 

the  instrument  along  its  axis, 
the  analyzer  being  at  A  and  the 
polarizer  at  B.     C  and  D  are 
— B    two    wedges   of   right-rotating 
quartz  with  parallel  sides  which 
are  movable  by  being  slid  past 
each  other   in   a   direction  at 
FlG   7<  right  angles  to  the  axis  of  the 

instrument   (AB).      Together, 

these  two  wedges  make  a  section  with  parallel  sides,  at 
right  angles  to  AB,  of  a  thickness  which  can  be  varied  at 
will  by  moving  one  or  both  of  the  wedges. 

E  is  a  section  of  left-rotating  quartz.  When  the  com- 
bined thickness  of  C  and  D  equals  that  of  E,  the  opposite 
rotating  effects  of  the  two  wedges  and  the  section  E  bal- 
ance, and  the  scale  of  the  saccharimeter  attached  to  the 
wedges  reads  zero.  If,  however,  a  tube  of  sugar  solution 
is  placed  in  the  instrument  between  the  polarizer  and  the 

1  See  table  of  the  comparative  rotatory  dispersion  of  quartz  and  sugar  solu- 
tion in  Landolt  (p.  133). 


THE   SACCHARIMETER  33 

compensating  device,  it  will  be  necessary  to  decrease  the 
thickness  of  the  right-rotating  section  made  by  the  wedges 
by  sliding  them  by  each  other  outward  till  the  left-rota- 
tory effect  of  the  section  E  balances  the  combined  effect 
of  C,  Dy  and  the  sugar  solution.  If  the  100  point  of  the 
wedge  scale  shows  the  position  of  the  wedges  to  compen- 
sate for  the  rotary  effect  of  the  normal  weight  of  pure 
sugar  polarized  under  standard  conditions,  then  the  per- 
centage purity  of  any  sample  will  be  given  by  the  scale 
reading  if  the  usual  procedure  is  followed. 

The  Soleil-Duboscq  Saccharimeter. — About  1850,  Du- 
boscq  was  the  first  to  make  a  practical  quartz-wedge  sac- 
charimeter  for  commercial  testing.  The  Soleil-Duboscq 
saccharimeter  uses  the  transition-tint  quartz  plate  already 
described  for  its  end-point  device,  and  practically  elimi- 
nates the  disturbing  effects  of  colored  solutions  by  what  is 
known  as  the  "  sensitive  tint  producer,"  an  attachment  for 
producing  light  of  the  color  desired  to  overcome  the  dis- 
turbing tint  of  any  highly  colored  solution  by  combination 
or  interference.  It  consists  merely  of  a  third  Nicol  prism, 
ranged  to  be  rotated,  and  placed  between  the  eyepiece  and 
the  analyzer.  Between  these  two  prisms  is  a  section  of 
quartz  cut  perpendicular  to  its  optic  axis.  By  rotating  this 
tint-producing  prism,  any  tint  desired  can  be  made  in  the 
field.  This  effect  is  produced  in  the  passage  of  the  light 
from  the  analyzer  of  the  saccharimeter,  which  latter  in  this 
case  acts  as  a  polarizer  relative  to  the  prism  of  the  tint 
producer,  and  is  in  accord  with  principles  already  explained 
in  describing  the  sensitive  plate  in  a  previous  chapter. 
Obviously  the  tint  device  must  be  adjusted  for  each  colored 
solution  polarized. 


34  THE   SACCHARIMETER 

The  tint  is  so  chosen  as  to  make  a  background  for  show- 
ing to  best  advantage  the  color  change  in  the  transition- 
tint  plate,  so  that  very  delicate  variations  in  color  in  either 
half  of  the  field  can  be  noted  with  precision.  The  tint 
device  in  no  way  affects  the  measurement  of  the  sugar 
solution,  since  this  obviously  is  made  through  adjustment 
of  the  position  of  the  quartz  wedges  compensating  for  rota- 
tions which  take  place  between  the  two  fixed  Nicols,  the 
polarizer  and  analyzer  of  the  saccharimeter. 

£17    D 


FIG.  8.  —  DIAGRAM  OF  OPTICAL  PARTS  OF  SOLEIL-DUBOSCQ  SACCHARIMETER 
(eyepiece  and  condenser  lenses  not  shown). 

A .  Analyzer.  S.  Position  of  tube  of  sugar  solution. 

P.  Polarizer.  RQ.  Rotating  Nicol   and  quartz  in  eyepiece, 

CC.  Quartz  compensator.  for  producing  sensitive  tints. 

T.  Transition-tint  plate. 

The  normal  weight  of  the  Soleil-Duboscq  saccharimeter 
is  based  on  the  rotation  value  of  the  millimeter  section  of 
quartz,  but  is  usually  given  as  16.35  grams  instead  of 
16.32. 

The  Soleil-Ventzke-Scheibler  Saccharimeter.  —  The  nor- 
mal weight  of  16.3  grams  of  sugar  does  not  give  a  solution 
of  sufficient  concentration  to  show  variations  in  tint,  in 
measurements  on  the  Duboscq-Soleil  saccharimeter,  for  the 
ordinary  observer  to  distinguish  with  precision  differences 
corresponding  to  .1  per  cent  of  sugar  in  the  sample,  and 
as  this  was  demanded  by  modern  commercial  requirements, 
an  improved  instrument  was  designed  by  Scheibler,  which 
used  the  graduation  of  Ventzke,  the  100  point  being  at  the 
position  of  compensation  for  a  sugar  solution  of  the  density 


THE   SACCHARIMETER  35 

of  i.iooo  at  17.5°  referred  to  water  at  17,5°.  This  stand- 
ard has  been  more  conveniently  expressed  as  equivalent 
to  26.048  grams  of  sugar,  weighed  in  air,  and  made  up  to  a 
solution  of  100  Mohr  cubic  centimeters  at  17.5°,  and  gives 
.026  grams  for  producing  a  change  of  .1  per  cent  of  the 
scale,  instead  of  .016  of  the  old  standard,  quite  sufficient  to 
make  a  distinguishable  change  in  tint  at  the  end  point. 
Scheibler  also  improved  the  quartz-wedge  saccharimeter  in 
many  details  of  design,  greatly  increasing  its  practical 
efficiency. 

While  the  modern  transition-tint  saccharimeter,  the 
Soleil-Ventzke-Scheibler,  as  it  is  formally  designated,  is  a 
precise  instrument  in  the  hands  of  trained  observers,  and 
still  much  used,  it  has  been  largely  replaced  in  the  past  few 
years  by  the  shadow  saccharimeter ;  for,  as  already  noted, 
any  transition-tint  instrument  is  useless  to  the  color-blind, 
and  requires  much  more  practice  to  read  with  precision. 

The  Schmidt  and  Hansch  Half-shade  Saccharimeter. - 
This  differs  from  the  modern  transition -tint  instrument  in 
using  the  Jellet-Cornu  prism  for  an  end-point  device. 
Consequently,  the  observer  determines  the  end  point  by  an 
equality  of  shade  instead  of  tint.  This  type  represents  the 
best  modern  saccharimeter.  With  such  an  instrument, 
using  ordinary  artificial  light,  the  intensity  being  much 
greater  than  the  sodium  flame,  the  objections  to  the  Jellet- 
Cornu  prism,  mentioned  in  describing  the  Duboscq  (rota- 
tory) polariscope,  do  not  apply,  as  the  prism  can  be  cut  to 
give  sufficient  precision  without  impairing  the  illumination 
too  greatly.1 

1  Some  of  the  most  recent  instruments  of  Schmidt  and  Hansch  use  the 
Lippich  double-shade  polarizer  and  an  improved  arrangement  of  illuminating 


36  THE   SACCHARIMETER 

The  Triple-shade  Saccharimeter. — The  triple-shade  de~ 
vice  of  the  Lippich  polariscope,  recently  applied  to  quartz- 
wedge  saccharimeters,  is  becoming  popular,  as  it  gives 
according  to  some  authorities  a  more  precise  end  point  (to 
.03  per  cent),  but  it  considerably  complicates  the  instru- 
ment, and  is  liable  to  get  out  of  adjustment.  It  is  doubtful 
whether  usual  conditions  permit  this  greater  precision  to 
be  of  avail.  Moreover,  an  expert  can  easily  read  the  half- 
shade  type  to  .03  per  cent.1 

Peters  Saccharimeter.  —  The  Peters  instrument  with  the 
Lippich  shade  device  differs  in  the  main  from  the  Schmidt 
and  Hansch  2  in  the  mounting,  which  is  designed  for  great 
stability  and  rigidity.  In  the  latest  instruments  the  wedges 
are  inclosed  in  a  dust-proof  box  which  also  mitigates  the 
effect  of  sudden  temperature  variations.  The  pinion  for 
moving  the  wedges  is  lengthened  so  that  the  observer  can 
move  it  with  his  hand  resting  on  the  table,  a  small  detail 
which  greatly  adds  to  the  comfort  of  manipulation. 

Instead  of  the  ivory  scales  used  in  the  earlier  instru- 
ments, both  the  Schmidt  and  the  Peters  saccharimeters 
are  now  fitted  with  scales  of  an  alloy  known  as  "nickelin," 

lens  as  recommended  by  Landolt  ("  Das  optische  Drehungsvermogen,"  p.  344). 
These  instruments  have  an  improved  form  of  compensator  devised  by  Martens 
{Zeits.  lustrum.,  20,  82),  consisting  of  two  quartz  wedges  corresponding  to  C 
and  D  of  Fig.  7,  but  of  opposite  rotations.  On  the  shorter  fixed  wedge  (Z?) 
is  cemented  a  prism  of  glass,  of  the  same  dispersion  as  quartz,  which  serves  to 
keep  the  rays  in  alignment  with  the  optical  axis  of  the  instrument.  The  ad 
vantages  gained  are  less  loss  of  light  by  absorption  and  a  saving  of  one  quart, 
section,  which  is  a  consideration  of  some  importance,  as  there  is  hardly  an 
adequate  supply  of  quartz  sufficiently  optically  pure  to  meet  the  demand  fo* 
saccharimeters. 

1  By  "  per  cent "  is  meant  the  scale  division  corresponding  to  a  per  cent. 

2  Schmidt  and  Hansch  have  adopted  this  form  of  mounting  in  some  of  their 
newer  saccharimeters. 


THE  SACCHARIMETER  37 

which  is  unaffected  by  moisture  and  so  little  by  tempera- 
ture as  to  make  any  change  in  the  divisions  negligible.1 

The  Double- wedge  Saccharimeter.  —  The  compensation 
system  of  these  saccharimeters  has  both  quartz  sections 
made  variable  by  sliding  wedge  devices.  The  wedges  are 
arranged  as  in  the  diagram. 

A  and  B  are  right-rotating  quartz  wedges,  corresponding 
to  those  in  the  ordinary  single-wedge  instrument ;  Cand  D 
are  the  left-rotating  quartz  wedges.  B  and  Care  movable, 


B       C 

A 


FIG.  9. 

the  first  known  as  the  "working  wedge,"  the  second  as  the 
"control  wedge."  Both  pairs  of  wedges  are  provided  with 
scales  of  equal  saccharimetric  value. 

In  ordinary  use  of  the  saccharimeter,  the  control  wedge 
is  set  at  zero,  and  the  working  wedge  is  used  in  the  ordi- 
nary manner  for  making  saccharimetric  measurements. 
On  removing  the  tube  of  sugar  solution,  the  control  wedge 
can  be  used  to  check  the  readings,  because  if  compensa- 
tion is  now  made  by  moving  this  wedge,  —  without  disturb- 
ing the  working  wedge  from  the  setting  for  the  reading 
first  taken,  —  both  wedges  will  give  equal  readings.  So, 
too,  when  no  rotating  solution  is  in  the  instrument,  the 
end  point  will  be  obtained  when  both  wedges  have  the 

1  Fric  uses  a  milk-glass  scale  illuminator  for  making  the  metal  graduations 
clearer.  Some  recent  instruments  have  the  graduations  engraved  on  the 
quart/,  of  the  compensator  itself. 


38  THE   SACCHARIMETER 

same  readings  at  any  point  of  the  scale.  The  double- 
wedge  compensation,  consequently,  enables  the  readings 
of  the  saccharimeter  to  be  checked  throughout  the  scale, 
as  well  as  giving  a  check  on  the  observation  itself. 

The  greater  complication  and  expense  of  the  double- 
wedge  saccharimeter  prevents  its  general  use. 


FIG.  10.  —  RECENT  TYPE  OF  PETERS  DOUBLE-WEDGE  HALF-SHADE 
SACCHARIMETER. 


RK,   Reflecting  device  for  illuminating  scale. 


G>  Box  inclosing  wedge  compensator. 


ACCURACY   OF   SACCHARIMETER 
MEASUREMENTS 

Weight.  —  Taking  the  limit  of  error  of  commercial  labo- 
ratory measurements  as  .1  per  cent,  it  is  clear  that,  as  no 
saccharimeter  in  general  use  has  a  normal  weight  of  less 
than  16  grams,  weighings  to  .005  gram  are  certainly  suffi- 
ciently precise.  The  most  appropriate  balance  for  weigh- 
ing sugar  samples  is  a  quickly  working  balance  of  the 
necessary  sensitiveness  only.  Indeed,  the  use  of  an  ana- 
lytical balance  of  high  precision  often  leads  to  more  inac- 
curate readings,  as  many  commercial  samples  contain  so 
much  moisture  that  the  loss  by  evaporation  is  considerable 
if  the  weighing  is  prolonged. 

Tube-length. — An  accuracy  of  length  to  .1  millimeter 
is  obviously  sufficient  for  all  ordinary  laboratory  measure- 
ments where  the  2-decimeter  tube  is  used.  Tubes  of  stand- 
ard makes  rarely  show  errors  of  length  as  great  as  this. 

Volume.  —  The  cubic  centimeter,  according  to  the  abso- 
lute metric  standard,  is  defined  with  sufficient  exactness 
as  equivalent  to  the  volume  occupied  by  i  gram  of  water 
weighed  in  vacuo  at  the  temperature  of  maximum  density, 
4°  C.1  Some  saccharimeters  are  graduated  for  a  normal 
weight  of  26.048  grams  of  sugar  dissolved  in  100  true 
(absolute)  cubic  centimeters.  Almost  universally  the  stand- 

1  The  term  "  milliliter  "  has  been  applied  to  this  unit  to  distinguish  it  from 
the  cube  whose  edge  is  I  centimeter. 

39 


4O        ACCURACY   OF   SACCHAR1METER   MEASUREMENTS 

ard  of  volume  used  in  saccharimeter  graduation  is  the 
cubic  centimeter  as  modified  by  Mohr,  which  in  this  case 
can  be  defined  as  the  volume  occupied  by  i  gram  of  ivater 
weighed  in  air  zvith  brass  TV  eights  at  a  temperature  of 
17.5°  C.  As  the  loo-cubic-centimeter  Mohr  flask  holds 
100.234  true  cubic  centimeters,  saccharimeters  graduated 
by  the  different  standards  vary  in  actual  rotation  magni- 
tudes of  the  scale  divisions  by  .234  per  cent 

This,  if  not  understood,  will  make  confusion  when  sac- 
charimeters of  the  two  different  graduations  are  compared 
with  reference  to  the  actual  magnitude  of  the  divisions  by 
standard  quartz  plates,  or,  if  the  appropriate  measuring 
flasks  are  not  used,  in  "  polarizing  "  samples. 

Evidently,  flasks  should  be  correctly  graduated  within 
.05  cubic  centimeter. 

Errors  of  Instrument.  Eccentricity.  —  In  rotatory  polari- 
scopes,  as  in  all  instruments  giving  angular  measurements, 
errors  are  due  to  the  axis  of  the  rotating  part  of  the  appa- 
ratus not  being  exactly  coincident  with  the  centre  of  the 
circle  on  which  the  scale  is  graduated. 

This  error  can  be  eliminated  in  instruments  having 
scales  extending  over  the  whole  circle  of  rotation  in  the 
usual  way,  by  measuring  the  angle  of  rotation  in  opposite 
quadrants,  that  is,  taking  the  mean  of  a  and  a  +  180°,  for 
it  will  be  remembered  that  the  end-point  phenomena 
repeat  themselves  at  points  180°  distant. 

The  "eccentricity"  of  a  polariscope  of  good  make  is 
rarely  more  than  the  limit  of  error  of  the  readings,  but 
occasionally  the  scale  disks  of  polariscopes  become  bent 
by  some  accident  so  that  errors  of  more  than  4'  may  be 
due  to  this  cause. 


ACCURACY  OF   SACCHARIMETER   MEASUREMENTS        41 

Errors  of  Quartz-wedge  Saccharimeters. — The  correct- 
ness of  the  saccharimetric  scale  can  be  established  at  a 
few  points  by  comparisons  with  standard  quartz  plates  of 
known  rotation.1  A  much  more  thorough  method  of  cali- 
bration, which  permits  all  points  of  the  scale  to  be  stand- 
ardized, is  by  use  of  the  "  control  tube."  The  control  tube 
is  telescoping  and  is  adjustable  to  variations  of  length 
through  a  range  of  about  100  millimeters,  its  exact  length 
at  any  position  of  adjustment  being  measured  by  a  scale 
reading  to  .1  millimeter.  As  the  readings  of  the  saccha- 
rimeter  are  directly  proportional  to  the  tube-length,  it  is 
possible  by  means  of  a  few  sugar  solutions  of  appropriate 
strength  to  verify  any  reading. 

Since  the  reading  (R)  gives  the  per  cent  (P)  of  sugar 
when  /=  2,  2/=  100,  and  w'  is  the  normal  weight  (N),  the 

equation  for  the  per  cent  of  sugar  when  any  length  of  tube 

/^ 
is  used  is  P=R  -,  and  the  reading  for  any  length  of  tube 

will  be  expressed  byR  =  P—     If  the  normal  weight  of 

. 

chemically  pure  sugar  is  used,  R  = Knowledge  of 

the  concentration  of  the  sugar  solution  used  is  not,  how- 
ever, necessary,  if  the  solution  is  concentrated  enough  so 
that  a  length  (L)  can  be  found  which  will  by  experiment 
for  the  solution  used  give  a  reading  of  100  on  the  saccha- 
rimetric scale,  the  correctness  of  this  point  having  been 
previously  verified  by  a  standard  quartz  plate,  since,  obvi- 

1  The  values  stamped  on  the  plate  mountings  are  not  always  reliable. 
Quartz  plates  can  be  exactly  standardized  by  sending  them  to  the  United 
States  Bureau  of  Standards,  Washington,  D.C.,  which  does  this  work  for  a 
small  fee. 


42        ACCURACY   OF   SACCHARIMETER   MEASUREMENTS 
ously,  any  reading  (R)  will  be  given  when  the  tube  is  of 

r>  r 

a  length ,  or  the  reading  at  any  tube-length  (/)  will  be 

i  oo  . 

expressed  by  the  following  equation,  R  =  — —    Thus,  the 

j^/ 

actual  reading  at  any  position  of  the  wedge  can  be  com- 
pared with  that  calculated  by  the  formula. 

Zero  Error.  —  In  common  with  most  measurements, 
polariscope  readings  must  be  corrected  for  "  zero  error," 
which  is  the  difference  in  scale  divisions  between  the  scale 
reading  at  the  observed  end  point  and  the  zero  of  the 
scale,  when  observations  are  taken  with  no  optically  active 
substance  in  the  instrument. 

Personal  Errors  of  Observer.  —  In  all  exact  measure- 
ments, the  influence  of  the  personal  errors  of  the  observer 
are  diminished  as  much  as  possible  by  averaging  the  results 
of  several  readings.  In  comparing  the  work  of  two  ob- 
servers, however,  it  must  not  be  forgotten  that  consider- 
able differences  may  be  shown  if  the  readings  of  each  are 
uncorrected  by  the  zero  error  obtained  by  the  observer 
himself.  The  results,  while  differing  appreciably  in  the 
actual  readings,  should,  on  applying  the  zero  corrections,  be 
found  to  be  concordant.  Each  observer  unconsciously 
uses  a  slightly  different  end  point,  which  does  not  affect 
the  accuracy  of  his  observations,  provided  the  same  end 
point  is  recognized  at  zero  and  at  the  position  of  rotation 
measured. 

Distortion  of  Cover  Glasses  of  Polariscope  Tubes.  —  If  the 
caps  of  polariscope  tubes  are  screwed  on  too  tightly,  so  as 
to  produce  a  strain  in  the  glass,  the  unequal  distribution  of 
density  may  cause  a  rotating  affect  on  the  light  rays  and 
so  make  error.  With  the  earlier  forms  of  tubes,  this  was 


ACCURACY  OF  SACCHARIMETER   MEASUREMENTS        43 

not  unusual ;  but  with  the  modern  types,  with  fine-threaded 
screws  and  soft  rubber  washers  back  of  the  glasses,  error 
from  this  cause  is  rare. 

Laurent  has  devised  tube  caps  with  bayonet  catch  and  a 
light  spring  which  makes  it  impossible  to  exert  undue 
pressure.  Landolt  accomplished  the  same  object  by  caps 
which  are  held  on  by  the  friction  of  ground  joints.  The 
Laurent  type  is  hard  to  keep  clean  and  free  from  corro- 
sion, while  the  Landolt  tubes  are  more  liable  to  leakage 
than  the  screw  cap,  which  is  the  most  practical  form  and 
almost  universally  used. 

Variations  from  Standard  Temperature.  —  Saccharime- 
ters  are  graduated  to  read  correctly  at  17.5°  C.,  it  being 
assumed  that  the  solution  is  made  up  at  the  standard 
temperature.  Almost  always  the  temperature  of  modern 
laboratories  is  higher  than  this.  The  effect  of  this  higher 
temperature  on  the  reading  is  a  complicated  one.  The  slight 
increase  in  the  reading,  rarely  amounting  to  more  than  a 
few  hundredths  of  a  division,  due  to  the  linear  expansion  of 
the  tube,  is  partially  compensated  for  by  the  slight  increase 
in  volume  of  the  flask  caused  by  the  expansion  of  the  glass. 

The  greatest  influence  caused  by  temperature  change  is 
on  the  specific  rotation  of  the  sugar,  which  decreases  with 
temperature  increase.  Andrews  has  found  that  when  a 
sugar  solution  is  made  up  to  the  normal  concentration  and 
polarized  at  a  temperature  greater  than  17.5°  C.,  the  read- 
ings are  too  low,  in  the  case  of  a  rotatory  saccharimeter, 
by  .00018  of  their  value  for  every  degree  of  temperature 
above  the  standard. 

This  assumes  that  all  apparatus,  flask,  tube,  and  sac- 
charimeter, as  well  as  the  water  used  in  making  up  the 


44        ACCURACY   OF   SACCHARIMETER   MEASUREMENTS 

solution,  are  at  the  same  temperature.  In  the  case  of  the 
quartz-wedge  saccharimeter,  a  greater  error  is  introduced, 
owing  to  the  increase  in  specific  rotation  of  the  quartz 
wedges  by  temperature  increase.1  Andrews  found  that 
the  correction  for  quartz-wedge  saccharimeters  was  .00030 
per  degree  above  standard  temperature.  Wiley2  has  con- 
firmed this  latter  correction  more  recently  by  an  investiga- 
tion covering  temperatures  from  o°  to  40°  C.  Investigators 
of  the  United  States  Coast  and  Geodetic  Survey  had 
arrived  at  practically  the  same  correction  value  as  early  as 
1890.  The  coefficient  calculated  from  Schonrock's  recent 
values  is  somewhat  higher. 

It  must  be  understood  clearly  that  correction  for  tem- 
perature can  only  be  made  when  the  temperature  condi- 
tions are  constant.  Especially  in  the  case  of  quartz-wedge 
saccharimeters,  such  corrections  may  be  quite  fallacious  if 
there  is  considerable  temperature  variation  during  the  day, 
as  the  quartz  wedges,  which  are  the  parts. of  the  instru- 
ment most  affected,  assume  the  outside  temperature  very 
slowly,  owing  to  their  thickness  and  poor  conductivity.3 
Constant  temperature  conditions  are  vital  for  accurate  sac- 
charimetric  work. 

Although  these  values  for  temperature  correction  seem 
well  established  by  careful  investigation,  they  are  disputed  by 
some,  and  have  not  yet  been  applied  in  commercial  testing. 

1  Technology  Quarterly,  1889,  p.  367.     Id.,  p.  373. 

2/.  Am.  Chem.  Soc.,  1899,  p.  568. 

3  Variations  of  considerable  magnitude  occur  in  polariscope  readings 
caused  by  temperature  changes  apparently  due  to  the  displacement  of  the 
optical  parts  by  the  expansion  or  contraction  of  the  metal  in  the  mounting  of 
the  instrument.  These  manifest  themselves  in  the  zero  error,  which  should 
be  frequently  taken  during  temperature  changes. 


ACCURACY   OF   SACCHARIMETER   MEASUREMENTS        45 

Quartz  plates,  when  properly  mounted,  always  give  con- 
stant readings  on  the  quartz-wedge  saccharimeter  at  all 
ordinary  temperatures,  provided  that  the  quartz-wedge  com- 
pensator system  and  the  plate  are  at  the  same  temperature. 
Obviously,  the  temperature  changes  affecting  the  rotation 
will  be  alike  in  the  plate  and  compensator.  On  this 
account,  quartz  plates  are  the  most  convenient  for  standard- 
izing this  type  of  saccharimeter,  as  control-tube  standard- 
ization requires  most  careful  temperature  correction  if  the 
sugar  solutions  are  not  made  up  and  polarized  at  the 
standard  temperature.1 

Most  sugar  chemists  have  adopted  the  recommendations 
of  the  International  Commission  for  Uniform  Methods  in 
Sugar  Analysis,  and  agreed  to  make  all  polarizations  at  20°. 

In  the  case  of  instruments  measuring  the  angle  of 
rotation  of  the  quartz  plate  directly  (rotatory  polariscopes), 
the  coefficient  of  increase  of  rotation  for  every  centigrade 
degree  of  temperature  above  standard  is  .000143. 


1  Commercial  saccharimeters  used  for  valuing  raw  sugars  and  molasses  are 
usually  standardized  by  means  of  carefully  corrected  quartz  plates  of  values 
approximating  within  a  few  per  cent  the  polarization  of  the  sugar  to  be  tested. 
The  reading  of  the  plate  given  by  the  instrument  is  carefully  corrected  to  the 
true  value  of  the  plate,  and  this  correction  applied  to  the  polarization  of  the 
sample,  the  zero  error  being  ignored.  By  this  method  of  correction,  the  dif- 
ference in  actual  magnitude  of  the  scale  divisions  of  instruments  graduated  in 
true  or  Mohr  cubic  centimeters  is  negligible,  provided  the  readings  of  the 
standard  quartz  and  the  sample  polarized  do  not  differ  more  than  4  or  5  per 
cent,  for  in  that  interval  a  variation  of  less  than  .3  per  cent  in,  say,  5  divisions 
would  make  an  error  of  only  .015,  which  is  obviously  well  within  the  error  of 
observation.  Even  a  sugar  polarization  varying  20  divisions  from  the  standard 
plate  value,  if  the  saccharimeter  were  standardized  to  that  value  independently 
of  its  zero  error,  would  be  correct  within  .06  ;  if,  for  instance,  a  Mohr  cubic 
centimeter  flask  were  used  instead  of  a  true  cubic  centimeter  flask  in  making 
'  up  the  solution. 


46        ACCURACY  OF   SACCHARIMETER   MEASUREMENTS 

The  scale  of  graduation  for  quartz-wedge  saccharimeters 
(almost  universal  throughout  the  commercial  sugar  world) 
being  that  for  26.048  grams  of  sugar  dissolved  in  100 
MoJir  cubic  centimeters  (the  original  Ventzke  scale),  Herz- 
feld  has  calculated  the  normal  weight  for  this  original 
and  standard  scale,  when  the  sugar  is  made  up  to  100  trite 
cubic  centimeters  ("  milliliters  ")  and  polarized  at  the  more 
convenient  temperature  of  20°,  to  be  26.01  grams. 

This  calculation  can  be  expressed  by  the  following 
equation : 


N  =— -  —  26.o48[i+(20-  I7.5).oooi43] 
^.234  j 


(i  —(20—  I7.5).ooo2i7/ 

The  part  in  the  brackets  represents  the  increase  in 
rotatory  power  of  the  quartz  in  the  compensator  of  the 
saccharimeter  due  to  the  difference  in  temperature  between 
17.5°  and  20°,  necessitating  a  proportional  increase  in  the 
normal  weight.  The  last  member  in  the  parenthesis  shows 
the  decrease  in  rotatory  power  of  the  sugar  caused  by  the 
higher  temperature.1 

The  International  Commission  has  decided  to  use  the 
even  value  26.00.  The  difference  of  .01  gram,  amounting 
to  .04  per  cent,  may  be  of  no  consequence  in  ordinary  com- 
mercial work,  but  is  hardly  in  accord  with  the  recom- 
mendation of  the  Commission  to  weigh  all  samples  to  .001 
gram,  or  to  .004  per  cent. 

The  official  saccharimetric  standard  adopted  by  the 
United  States  Customs2  is  26.048  grams,  weighed  in 

1  Zeitschr.  Analyt.  Chem.  38,  A.  V.  u.  E.  22. 

2  United  States  Treasury  Document  No.  2113,  Division  of  Customs,  p.  16. 


ACCURACY  OF   SACCHARIMETER    MEASUREMENTS        47 

vacuo,  and  dissolved  in  100  true  cubic  centimeters,  all 
solutions  being  made  and  polarized  at  17.5°. 

Apparently  all  Schmidt  and  Hansch  saccharimeters 
sent  to  the  United  States  subsequently  to  about  1892,  and 
having  a  serial  number  above  3200,  are  graduated  for 
26.048  grams  of  sugar  in  100  true  cubic  centimeters  to 
conform  to  this  standard.  (See  footnote  No.  2.)  The 
Peters  saccharimeters  examined  by  the  author  have  been 
standardized  on  the  original  Ventzke  scale. 

Special  errors  peculiar  to  commercial  saccharimetry  will 
be  discussed  under  the  descriptions  of  commercial  sugar 
polarizations. 


GENERAL   NOTES   ON  APPARATUS   AND 
LABORATORY   MANIPULATION 

Installation.  —  The  laboratory  for  polariscopic  testing 
should  be  kept  at  as  nearly  a  constant  temperature  as 
possible,  preferably  20°,  and  therefore  be  well  ventilated, 
and  of  sufficient  size  not  to  be  affected  by  the  heat  of 
lamps.  Polariscope  apparatus  should  be  so  installed  that 
the  observer  is  screened  from  outside  light. 

This  is  done  sometimes  by  placing  the  polariscope  in  a 
separate  darkened  room,  the  light  passing  into  the  instru- 
ment through  a  hole  in  a  partition  from  a  lamp  outside, 
appropriate  means  of  illumination  of  scales  being  by  re- 
flectors or  small  electric  or  gas  lights.  The  more  con- 
venient method  is  to  place  the  apparatus  in  a  large,' well- 
ventilated  hood,  so  located  in  a  shaded  part  of  the  room 
that  the  direct  light  cannot  enter,  the  necessary  illumina- 
tion being  arranged  as  described. 

The  polariscope  should  be  screened  from  the  direct  heat 
of  the  lamps  by  glass  plates  or,  better,  absorption  cells 
filled  with  water. 

Care  of  Instruments.  —  Like  many  instruments  of  preci- 
sion, polariscope  apparatus  is  extremely  sensitive  to  de- 
rangement from  careless  handling.  Polariscopes  should  be 
disturbed  as  little  as  possible  beyond  the  usual  manipula- 
tion of  testing.  Nicol  prisms,  from  the  nature  of  their 
material,  are  peculiarly  liable  to  injury.  Calc-spar,  being 


APPARATUS  AND   LABORATORY   MANIPULATION   NOTES       49 

much  softer  than  glass,  is  easily  scratched  by  careless 
handling  or  cleaning.  Its  peculiar  crystallization  makes  it 
liable  to  split  from  rapid  changes  of  temperature,  as  in 
overheating  by  placing  the  instrument  too  close  to  the 
lamp.  Calc-spar  is  easily  corroded  by  acids  caused  by 
fermentation  of  sugar  solutions  carelessly  spilled  in  the 
instrument.  With  proper  care,  polarizing  apparatus  will 
last  a  lifetime.  As  the  accuracy  of  the  sugar  chemist's  work 
is  dependent  on  the  precision  of  the  instrument,  daily  prac- 
tice in  such  care  as  will  insure  this  precision  is  obviously 
a  necessary  part  of  the  knowledge  and  duties  required  of 
every  worker  in  a  sugar  laboratory. 

Handle  the  instrument  with  clean  hands.  See  that  the 
flame  of  the  lamp  is  about  200  millimeters  (the  length  of 
an  ordinary  polariscope  tube)  from  the  end  of  the  instru- 
ment. This  avoids  overheating,  which  not  only  endangers 
the  prisms,  but  throws  the  instrument  out  of  adjustment. 
With  most  types,  it  also  insures  an  evenly  illuminated  field 
of  maximum  brightness,  as  the  foci  of  the  condensing 
lenses  are  adjusted  for  this  distance.  Only  when  absolutely 
necessary,  clean  lenses,  quartz  wedges,  and  cover  glasses 
with  perfectly  clean  filter  paper  or  linen  cloth,  never  with 
silk  or  chamois,  as  the  rough  surfaces  of  these  fabrics  are 
liable  to  hold  grit.  Always  rub  very  lightly.  In  cases 
where  the  edges  cannot  be  reached,  remove  dirt  very 
carefully  with  a  clean,  pointed  stick  of  soft  wood,  as  a 
toothpick. 

Clean  Nicol  prisms  with  special  care,  and  only  when 
absolutely  necessary.  In  the  best  instruments,  Nicol  prisms 
are  protected  by  cover  glasses  where  they  would  other- 
wise be  exposed. 


50       APPARATUS  AND    LABORATORY   MANIPULATION  NOTES 

Polariscope  Lamps.  —  Many  forms  of  sodium-light  lamps 
have  been  devised.  Most  of  them  use  ordinary  table  salt, 
which  is  best  adapted  for  the  purpose,  the  other  common  salts 
of  sodium  not  volatilizing  so  readily,  and  consequently  giv- 
ing less  intense  light.  Sodium  carbonate  works  reasonably 
well,  but  causticizes  to  a  considerable  extent,  forming  a 
corrosive  liquid  which  drops  down  and  fouls  the  apparatus. 
Sodium  bromide  is  said  to  produce  a  more  intense  light 
than  the  chloride,  but  gives  off  bromine  vapors  which  are 
liable  to  injure  the  polariscope.  Landolt  uses  cylinders 
of  salt  which  are  fused  on  small  forms  made  of  nickel  wire 
netting.  Wiley  has  devised  a  clockwork  lamp  by  which 
the  salt  is  fed  into  a  Bunsen  flame  from  opposite  sides  by 
means  of  two  slowly  revolving  wheels  of  platinum  gauze 
which  dip  into  dishes  holding  a  salt  solution.  The  author 
has  preferred  the  ordinary  type  of  lamp,  which  consists  of  a 
Bunsen  burner  so  adjusted  as  to  burn  with  as  strong  an 
air  blast  as  possible,  this  being  a  requisite  for  any  lamp 
giving  intense  light.  The  salt  is  exposed  to  the  flame  in  a 
platinum  or  nickel  gauze  spoon,  which  is  heated  in  the 
mantle  just  outside  the  luminous  cone, — the  hottest  part 
of  the  flame.  The  intensely  bright  yellow  sodium  vapor 
is  then  carried  by  the  blast  well  above  the  blue  cone  of  the 
flame,  the  light  of  which  latter  should  be  cut  out  of  the 
polariscope  field  by  a  diaphragm  attached  to  the  lamp.  A 
mixture  of  table  salt  with  sodium  phosphate,  as  recom- 
mended by  Dupont,  fuses  upon  the  gauze  and  does  not  de- 
crepitate as  salt  does  alone.  A  mixture  of  these  powdered 
salts  made  into  a  paste  with  a  little  glycerine  has  been 
found  very  convenient  for  applying  to  the  gauze  with  a 
small  platinum  spatula, 


APPARATUS  AND   LABORATORY    MANIPULATION  NOTES       51 


Quite  recently  the  author  has  adopted  a  simple  type 
of  sodium  lamp  which  has  proved  by  far  the  most  con- 
venient and  efficient.  A  shallow  boat,  made  by  folding  up 
a  rectangular  piece  of  platinum  foil  and  welding  together 
the  ends  by  hammering  at  a  red  heat,  is  used  to  hold  the 
salt.  The  boat  is  of  such  shape  as  to  spread  the  flame  of 
a  Tirrill  burner,  which  impinges  against  the  polished  plati- 
num, after  the  manner  of  a  batwing  flame.  The  salt  which 
is  liquefied  creeps  up  the  sides  of  the  boat,  and  is  vaporized 
in  the  flame  sheet,  giving  a  very  brilliant  and  steady  light 
which  lasts  for  fifteen  minutes  or  more  without  renewing 
the  salt. 

The  flame  shoots  off  obliquely,  thus  exposing  more  light 
surface  in  the  axis  of  vision.  From  time  to  time  lumps  of 
salt  (which  have  been  previously  fused)  are  added  till  the 
boat  is  again  filled  with  liquid. 

The  diagrams  explain  the  apparatus,  the  exact  adjust- 
ment of  the  position  of  the 
platinum  boat  being  easily 
determined  by  experiment. 

A  more  elaborate  but 
somewhat  more  efficient 
boat  for  holding  the  salt  is 
shown  in  Figure  1 2.  A  piece 
of  platinum  foil  is  folded 
double  in  such  a  way  as  to 
make  a  double-bottomed 
boat,  the  edges  of  the  folded 
sheet  making  a  narrow  slit 
along  one  edge  of  the  boat.  The  inner  bottom  is  perfo- 
rated. In  this  form  the  liquefied  salt  rises  by  its  capil- 


B 

B 

\ 

^ 

I 

Side  Section                        Front 

FIG.    II. 

.    Boat.                      D.   Yellow  flame. 
.    Burner-tube.         F.   Diaphragm-opening. 
Blue  flame  cone. 

52       APPARATUS  AND   LABORATORY   MANIPULATION  NOTES 

larity  to  the  mouth  of  the  slit  and  is  taken  by  the  strong 
blast  of  the  lamp  up  into  the  flame  in  a  brilliant  sheet. 
Such  an  arrangement  has  given  a  constant  light  for  an 
hour  without  replenishing. 

The  platinum  boats  must  not  be  too  large,  or  the  mass 
of  metal  chills  the  flame  and  reduces  the  intensity  of  the 
plan  of  goat  light  appreciably.     It  may  be  needless 

— s^^^^^^^-    to  add  also  that   the   burner  must   be 
working  with  as  strong  an  air  blast  as 
N^y^-''  possible. 

Most  polariscopes  are  equipped  with 
a  plate  of  potassium  bichromate  crystal 
to  filter   out  extraneous  rays.     Landolt 
Boated  Burner          uses   an    absorption    cell   filled   with    a 
weak  solution  of  this  salt,  and  a  second 
cell  containing  a  solution  of  uranous  sulphate. 

For  the  quartz-wedge  saccharimeter,  any  strong  lamp- 
light serves.  The  Welsbach  light  is  particularly  good. 
Where  gas  cannot  be  had,  Welsbach  burners  can  be 
obtained  which  use  vaporized  kerosene  on  the  type  of  the 
"  Washington  "  light.1  Acetylene  and  incandescent  electric 
lights  are  often  used.  Schmidt  and  Hansch  have  per- 
fected an  electric  light  which  can  be  attached  to  their 
saccharimeters.  This  is  of  small  size  and,  while  giving 
light  of  great  intensity,  produces  very  little  heat. 

Balance.  —  For  ordinary  polariscope  work,  a  quick-work- 
ing balance  with  a  capacity  of  200  grams  and  sensitive  to 
.005  gram  is  preferable  to  the  more  precise  analytical  type. 
It  should  be  inclosed  in  a  glass  case.  Such  balances, 
known  as  "  sugar  balances,"  are  made  by  all  the  leading 

1  Used  by  the  writer  in  Porto  Rico. 


APPARATUS   AND   LABORATORY   MANIPULATION  NOTES       53 


manufacturers.  They  are  also  best  adapted  for  calibrat- 
ing most  volumetric  apparatus.  A  "  trip  scale "  with  a 
capacity  of  2  kilos  and  sensitive  to  .1  gram  is  indispensa- 
ble for  many  of  the 
laboratory  opera- 
tions incident  to 
preparation  of  so- 
lutions and  cali- 
brating the  larger 
volumetric  appa- 
ratus; while,  of 
course,  many  of 
the  more  delicate 
weighings  of  exact 


FIG.  13.  —  SUGAR-BALANCE. 


density  determina- 
tions  and  other 
gravimetric    measurements    require   a   delicate  analytical 
balance. 

Sugars  and  other  non-corrosive  substances  are  usually 
weighed  out  in  nickel  or  German  silver  dishes  provided 

with  a  lip  for  pouring. 
These  dishes  are  numbered 
and  provided  with  a  cor- 
respondingly numbered 

tare    weight.       The     sub- 
FIG.  14. -WEIGHING-DISH  AND  TARE      stance    js    dther   dissolved 
WEIGHT. 

directly  in  the  dish  by  rub- 
bing the  crystals  under  water,  using  a  metallic  pestle, 
or  washed  into  the  measuring  flask,  the  former  being  the 
usual  method. 

In  saccharimetric  work,  either  the  normal  or  half-normal 


54       APPARATUS  AND   LABORATORY   MANIPULATION  NOTES 

weight  is  taken,  brass  weights  of  this  value  being  furnished 
with  the  saccharimeter.  The  half-normal  weight  is  only 
used  when  the  sample  makes  a  dark  solution  not  readily 
clarified,  and  consequently  difficult  to  read  in  the  polari- 
scope,  such  as  a  low-grade  molasses,  for  instance.  [For 
Manipulation  of  Polariscope  Tubes,  see  p.  91.] 

Flasks.  —  The  loo-cubic-centimeter  flask  is  the  one 
most  conveniently  used.  Practically  all  commercial  sac- 
charimeters  are  graduated  for  solutions  made  up  to  100 
Mohr  cubic  centimeters,  the  unit  of  which  has  already 
been  defined  as  the  volume  occupied  by  i  gram  of  water 
at  a  temperature  of  17.5°,  weighed  in  air  with  brass 
weights.  Recently  there  has  been  a  strong  movement 
on  foot  among  the  chemists  of  all  nations  to  use  the  true 
centimeter  as  the  basis  of  measurement.  [See  p.  46.] 

Special  Laboratory  Apparatus.  —  Short-stemmed  funnels 
of  a  capacity  of  75  to  100  cubic  centimeters  have  been 
found  most  convenient  for  filtering  solutions  for  polarizing. 
These  funnels  are  placed  directly  on  heavy  glass  cylinders 
for  receiving  the  filtrate,  thus  obviating  a  separate  filter 
stand.  The  cylinders  have  a  lip  for  pouring,  and,  most 
conveniently,  a  capacity  of  100  cubic  centimeters.  Watch 
glasses  are  used  to  cover  the  funnels  to  prevent  evapora- 
tion during  filtering. 

Besides  the  ordinary  loo-cubic-centimeter  flasks,  those 
with  a  double  mark  on  the  neck,  one  at  100,  the  other  at 
no  cubic  centimeters,  as  well  as  similar  ones  marked  at 
50  and  55  cubic  centimeters,  are  used  in  special  operations, 
to  be  described  later. 

Clarifying  reagents,  such  as  basic  lead  acetate,  are  pref- 
erably stored  in  large  bottles  arranged  with  delivery  tubes 


APPARATUS  AND   LABORATORY   MANIPULATION  NOTES       55 

for  convenience  in  using.  The  delivery  tube  should  be 
connected  with  a  coarse  burette,  or,  what  is  more  cleanly, 
a  graduate  used  so  that  the  volume  of  the  reagent  added 
is  known  with  fair  accuracy.  This  is  important  in  some 
cases  where  corrections  are  to  be  made  for  errors  caused 
by  clarifying. 

A  similar  tubulated  bottle  of  large  capacity  should  be 
provided  for  the  water  used  in  making  up  solutions  which 
thus  can  be  maintained  at  laboratory  temperature.  A 
convenient  arrangement  is  to  equip  the  bottle  with  two 
delivery  tubes,  one  for  quick  delivery,  the  other  a  fine  jet 
for  filling  flasks  to  mark. 

Other  apparatus,  such  as  a  muffle  for  ash  determinations, 
drying  ovens,  etc.,  need  not  be  considered  here,  as  it  differs 
in  no  wise  from  that  used  in  general  food  chemistry. 

Immediately  after  use,  all  glass  apparatus,  as  well  as 
polariscope  tubes,  should  be  washed  in  running  water  and 
placed  on  racks  to  dry.  This  insures  a  sufficient  supply 
of  clean  and  dry  apparatus  at  all  times. 

Brix  Spindles.  —  Brix  spindles1  are  most  conveniently 
made  in  the  following  sizes:  0-5,  5-10,  10-20,  20-30,  or 
with  a  range  of  not  over  10°  for  the  higher  concentrations. 
They  should  be  equipped  with  thermometers,  and  not  be 
too  large  for  convenient  use,  not  over  12  or  14  inches  long. 
The  graduations  should  be  of  sufficient  size  to  permit  of 
easily  reading  to  .1°.  If  the  expansion  corrections  for 
17.5°  are  marked  on  the  thermometer  scales,  they  should 
be  figured  for  the  middle  Brix  reading ;  for  instance,  for 
a  10-20  hydrometer  the  expansion  corrections  should  be 
for  15°. 

1  Described  on  p.  117. 


56       APPARATUS  AND   LABORATORY   MANIPULATION   NOTES 

A  draining  rack  with  holes  for  holding  the  spindles 
should  be  provided,  or  pockets  made  of  copper  gauze, 
which  are  very  convenient. 

Calibration  of  Flasks. — Weigh  the  thoroughly  cleansed 
and  dried  flask  to  .005  gram.  Weigh  again  when  filled  to 
the  mark  with  freshly  distilled  water  of  known  tempera- 
ture. The  volume  of  the  flask,  in  Mohr  cubic  centimeters, 
can  be  computed  from  the  following  formula : 

v=P^l~'  000025(^-17.5)]; 

where  v  expresses  the  desired  volume  at  17.5°;  P,  the 
weight  of  water  in  grams  which  fills  the  flask  to  the  gradu- 
ation mark  at  the  temperature  /;  dy  the  density  of  water 
at  17.5°  C. ;  and  d'  the  density  of  the  water  at  temperature 
of  weighing.  These  density  values  are  obtained  from 
tables.  That  part  of  the  equation  which  is  inclosed  in 
brackets  expresses  the  correction  on  the  volume  caused  by 
the  expansion  of  the  glass  of  the  flask,  and  is  small  enough 
to  be  omitted  for  ordinary  calibrations  made  at  room  tem- 
peratures. 

Flasks  for  commercial  saccharimetry  are  usually  gradu- 
ated by  reading  the  lower  edge  of  the  meniscus  of  the 
water  surface  tangent  to  the  upper  edge  of  the  graduation 
mark  on  the  neck  of  the  flask,  when  the  whole  of  the 
meniscus  is  shaded.  This  is  done  by  holding  the  flask  up 
to  the  light  with  the  mark  on  a  level  with  the  eye,  or  look- 
ing at  the  mark  against  a  background,  made  by  a  piece  of 
white  paper,  held  in  strong  light  a  few  inches  back  of  the 
flask.  Care  must  be  taken  to  have  the  flask  neck  perpen- 
dicular if  the  flask  is  held  in  the  hand  while  reading  the 


APPARATUS   AND    LABORATORY    MANIPULATION   NOTES        57 

mark,  as  well,  of  course,  to  be  sure  that  the  neck  above  the 
water  surface  is  perfectly  dry.  If  there  are  adhering  drops, 
they  should  be  removed  completely  with  a  wisp  of  filter 
paper. 

True  cubic  centimeter  flasks,  as  has  been  stated  already, 
are  graduated  on  a  unit  which  is  the  volume  occupied  by 
i  gram  of  water  weighed  in  vacuo  at  its  maximum  density 
(4°).  The  weight  of  the  air  displaced  in  the  space  taken 
by  the  water  is  only  partially  balanced  by  the  air  displace- 
ment of  the  weights  in  the  other  pan  of  the  balance,  as  the 
volume  of  the  latter  is  less  than  one  eighth  as  large,  owing 
to  their  greater  density.  In  consequence  the  actual  mass 
of  the  water  weighed  is  expressed  by  a  value  somewhat 
more  than  .  I  per  cent  greater  than  its  apparent  weight  in 
air.  It  can  be  shown  that  the  true  mass  of  any  given 
volume  of  water  can  be  found  from  its  weight  in  air  with 
ordinary  weights  by  the  formula, 


where  W  is  the  weight  expressing  the  true  mass ;  Pt  the 
weight  actually  found  by  weighing  in  air  by  the  ordinary 
method;  cr,  the  density  of  air,  taken  as  .0012;  S,  the  den- 
sity of  water,  taken  as  i.oo;  and  A,  the  density  of  the 
balance  weights,  taken  as  8.4.  With  these  values,  which 
are  approximate  enough  for  flask  calibration,  the  value  of 

i  — —  )  is  .00106. 

S     A/ 

Moreover,  as  the  water  weighed  at  any  temperature 
other  than  4°  is  less  dense,  its  volume  is  greater  than  at 
the  standard  temperature. 


58       APPARATUS  AND   LABORATORY  MANIPULATION  NOTES 

Hence,  the  complete  formula  expressing  the  volume  of 
a  flask  in  true  cubic  centimeters  at  20°  when  the  water 
it  contains  is  weighed  in  the  ordinary  manner  at  the 
temperature  ty  is 


v  =     (P  +  .00106  P)  [i  -  .000025(7  -  20)]  ; 

where  d±  is  the  density  of  water  at  4°,  and  d*  the  density  at 
the  temperature  it  had  when  weighed. 

The  100  Mohr  cubic  centimeter  flask  used  in  saccha- 
rimetry  has  a  volume  of  100.234  true  cubic  centimeters. 
The  100  true  cubic  centimeter  flask  contains  99.766  Mohr 
cubic  centimeters. 

Flasks  should  be  numbered  (conveniently,  by  marking  on 
the  neck  with  a  diamond)  and  their  calibrations  recorded. 

Observations.  —  Before  taking  readings  see  that  the  field 
and  the  scale  are  properly  illuminated.  The  field  should 
be  as  evenly  and  brightly  lighted  as  possible  at  the  end 
point,  and  its  image  sharply  focused.  The  image  is 
focused  by  moving  the  eyepiece  in  or  out  in  its  telescop- 
ing sleeve. 

A  perfectly  defined  field  is  vital  for  precise  reading. 
Before  adjusting  focus  and  illumination  in  shadow  instru- 
ments, first  turn  the  analyzer  (or  in  quartz-wedge  compensa- 
tion instruments,  the  wedge  pinion)  so  that  the  scale  reads 
some  divisions  from  zero  to  get  the  full  volume  of  light. 
After  placing  the  tube  of  solution  in  the  instrument,  the 
focus  must  be  readjusted. 

Every  effort  should  be  made  to  have  solutions  for  polar- 
ization absolutely  clear.  It  is  advisable  to  filter  solutions, 
even  if  made  from  pure  substances,  as  even  a  slight  opal- 


APPARATUS   AND   LABORATORY   MANIPULATION  NOTES       59 

escence  due  to  minute  traces  of  foreign  matter  affects  the 
definition  of  the  image  and  consequently  seriously  affects 
the  precision  of  the  readings. 

Practice  rapid  readings,  averaging  the  results  of  several 
rather  than  fatigue  the  eye  by  long  observations.  Rapidly 
taken  readings,  if  taken  with  care,  are  more  accurate. 

The  room  temperature,  which  should  be  the  temperature 
of  the  apparatus  and  solutions,  should  be  recorded  at  the 
time  of  observation. 

End  Point.  —  (jShadow  instruments.")  After  setting  at 
zero  (by  the  scale),  manipulate  the  instrument  so  as  to 
move  the  shadow  slightly  from  one  side  of  the  field  to  the 
other  several  times,  confining  the  attention  to  the  central 
vertical  line.  Take  the  point  of  transition  of  the  shadow 
across  this  line  as  the  end  point  is  approached  from  opposite 
sides  of  the  field  in  different  observations.  This  is  theoreti- 
cally the  same  point  as  that  found  by  setting  the  instrument 
for  equal  illumination  of  both  halves  of  the  field,  but  is 
easier  for  most  observers.  This  method  also  enables  ac- 
curate readings  to  be  taken  in  certain  cases  where  dust, 
faulty  illumination,  imperfect  adjustment  of  prisms,  or  dis- 
persion variations  (in  wedge  saccharimeters)  make  it  im- 
possible to  get  both  halves  of  the  field  to  look  exactly  alike. 
Of  course  the  field  will  be  equally  illumined,  in  the  case 
of  a  shadow  instrument,  when  there  is  a  rotatory  effect 
approaching  90°  from  the  true  end  point,  but  no  shadow 
effect  will  appear,  as  already  noted.  The  general  approach 
toward  the  true  end  point  will  be  shown  by  the  rapid 
darkening  of  the  field  as  a  whole. 

If  separate  scale  lights  are  used,  they  should  be  kept 
turned  off  except  when  reading  the  scale,  to  prevent  heat- 


60       APPARATUS  AND   LABORATORY   MANIPULATION  NOTES 

ing  the  instrument.  Any  outside  glare  also  quickly  im- 
pairs the  sensitiveness  of  vision  in  precise  work. 

In  beginning  work  with  an  unfamiliar  instrument,  set 
the  scale  at  zero,  and  study  the  changes  of  field  about  this 
point.  This  is  better  than  hunting  blindly  for  what  you 
may  not  recognize,  with  possible  injury  to  your  eyesight 
if  not  to  the  instrument.  It  is  especially  important  to 
make  this  zero  setting  when  some  unusual  end  point  is 
observed,  as  in  the  Wild  polariscope.1 

Scale  Readings. — Always  correct  for  "zero  error "  (the 
difference  between  the  end  point  observed  as  read  on  the 
scale  and  the  zero  of  the  scale),  noting  whether  this  is  plus 
or  minus.  In  case  zero  error  is  not  large,  it  is  better  to 
allow  for  it  in  calculations  than  to  attempt  to  bring  the 
scale  into  perfect  adjustment  with  the  end  point.  Frequent 
determinations  of  zero  error  should  be  made,  especially  if 
the  temperature  is  changing. 

Take  the  average  of  at  least  six  readings  for  all  exact 
work,  rejecting  the  first  reading  if  it  shows  much  discrep- 
ancy from  the  others,  or  any  other  of  the  series  which  is 
clearly  wrong,  owing  to  some  circumstance  peculiar  to  that 
individual  observation,  and  not  affecting  the  others  of  the 
series,  as,  for  instance,  eye  fatigue,  which  passes  away  after 
a  moment's  rest. 

All  saccharimeter  scales  are  expressed  in  percentages 
and  tenths.  Polariscopes  measuring  rotations  directly,  ex- 
cept a  few  of  most  recent  type,  give  readings  in  degrees 
and  minutes.  Saccharimeter  scales  are  graduated  into 
divisions  expressing  per  cents,  rotatory  scales  into  halves 

1  Special  notes  on  the  use  of  instruments  of  different  types  are  given  in 
next  chapter. 


APPARATUS  AND   LABORATORY   MANIPULATION   NOTES       6 1 

or  thirds  of  a  degree.  In  both  cases,  values  smaller  than 
these  graduations,  expressed  as  fractions  of  the  smallest 
scale  division  into  which  the  scale  is  actually  graduated, 
are  determined  by  "  verniers."  A  vernier,  so-called  from 
its  inventor,  a  French  mathematician,  is  a  device  for  read- 
ing fractions  of  the  smallest  division  of  a  scale.  In  the 
form  used  in  polariscopes,  it  is  a  sliding  scale  parallel  to 
and  extending  along  the  main  scale,  graduated  in  both 
directions  from  the  zero  line  which  is  the  index  mark 
whose  position  the  main  scale  measures. 

Each  half  of  the  vernier  scale  extending  from  the  zero 
mark  has  a  length  which  is,  measured  in  smallest  divisions 
of  the  main  scale,  one  less  than  the  denominator  of  the 
fraction  which  the  vernier  is  designed  to  determine,  while 
this  length  of  the  vernier  scale  is  itself  divided  into  just 
the  number  of  parts  which  express  this  denominator. 

For  instance,  a  vernier  designed  to  divide  a  scale  divi- 
sion into  ten  equal  parts  is  itself  nine  scale  divisions  long, 
but  is  divided  into  ten  equal  parts.  Hence  in  this  example 
each  vernier  division  is  -£$  of  the  main  scale  division.  If 
the  zero  line  of  the  vernier  (which,  it  must  be  remembered, 
is  always  the  index  or  point  of  reference  of  the  main  scale) 
does  not  coincide  with  a  main  scale  division,  but  is  distant 
-£Q,  evidently  \hzfirst  line  of  the  vernier  scale  will  coincide 
with  the  next  main  scale  division  line.  If  the  zero  mark 
is  distant  tzvo  tenths  of  the  main  scale  division  interval 
from  a  line,  the  second  line  of  the  vernier  scale  will  coin- 
cide with  a  main  scale  line,  and  so  on. 

The  following  rules  can  be  given  for  vernier  readings : 

(i)  First  determine  the  fraction  of  the  scale  divisions 
which  the  vernier  expresses,  by  actually  counting  the 


62       APPARATUS   AND   LABORATORY   MANIPULATION  NOTES 

number  of  divisions  of  the  vernier  scale,  in  either  direction 
from  zero. 

(2)  Starting  from  the  zero  of  the  vernier  and  reading  in 
the  direction  of  the  main  scale  readings,  the  number  of 
the  line  of  the  vernier  scale  (counting  from  zero)  which 
coincides  with  a  line  of  the  main  scale  gives  the  number 
of  parts  of  the  scale  division  which  the  index  (zero  line 
of  vernier)  marks. 

Hence,  in  the  case  of  a  vernier  reading  tenths,  if  the 
zero  line  of  the  vernier  lies  beyond  the  twenty-sixtJi  main 
scale  division,  and  the  seventh  line  of  the  vernier  coincides 
with  a  line  of  the  main  scale,  the  reading  will' be  26.7. 


I  \ 

1 

1  f 

I  f 

f  I  r  i  i  i 

i  i 

III      I  I  II  1 

IJJ 

"I 

!  U 

TJ 

i 

TTi 

10 

0 

1G 

FIG.  15.  —  VERNIER  READING  26.7. 

When  the  zero  line  of  the  vernier  lies  on  the  minus  side 
of  the  scale,  the  lines  of  the  corresponding  side  of  the 
vernier  are  read.  On  rotatory  scales  of  polariscopes  in 
chemical  laboratories  verniers  usually  read  to  even  min- 
utes only,  half  degree  divisions  being  divided  into  fifteen 
parts,  thirds  of  a  degree  divisions  into  ten  parts.  In  read- 
ing rotatory  scales  the  number  of  divisions  marked  by  the 
zero  of  the  vernier  is  first  read  and  then  expressed  in 
degrees  and  minutes.  Not  until  this  is  done  should  the 
vernier  be  read  and  its  reading  added.  Study  system  of 
division  till  you  thoroughly  understand  it  before  taking 
readings. 

In  rotatory  instruments,  the  direction  of  rotation  is  abso- 


APPARATUS  AND   LABORATORY   MANIPULATION   NOTES       63 

lutely  determined  for  rotations  less  than  180°,  but  in  the 
case  of  a  quartz-wedge  saccharimeter,  where  the  actual 
direction  of  the  scale  readings  has  no  direct  reference  to 
that  of  the  rotation  of  the  plane  of  polarization,  the  plus 
direction  of  the  scale  is  sometimes  to  the  right  and  some- 
times to  the  left.  In  most  commercial  saccharimeters,  the 
plus  direction  is  to  the  right ;  in  some  of  the  old  instruments 
and  in  double-wedge  compensation  saccharimeters,  it  is  to 
the  left.  An  inspection  of  the  scale  will  always  make 
clear  which  is  the  plus  direction  of  the  readings,  for,  as 
the  scale  is  designed  for  measuring  sugar,  a  right  (plus) 
rotating  substance,  the  long  end  of  the  scale  will  be  the 
plus. 

Form  the  habit  of  checking  all  observation  by  taking  a 
final  reading  of  the  large  divisions,  independent  of  the 
vernier  reading.  This  practice  will  often  detect  errors, 
as  an  observer  naturally  tends  to  concentrate  his  attention 
on  the  more  difficult  vernier  reading,  and,  becoming  care- 
less of  the  reading  of  the  main  scale,  often  repeats  an 
error  once  made  throughout  the  whole  series  of  readings. 

Calculated  results  and  averages  should  be  carried  to  one 
decimal  beyond  that  expressing  the  limit  of  scale  reading, 
following  the  usual  practice  of  physical  measurements. 

Calculation  of  Errors  of  Analysis.  —  It  would  seen  super- 
fluous to  call  attention  to  the  importance  of  calculating  the 
influence  of  the  errors  of  measurements  on  the  accuracy 
of  polarimetric  determinations,  were  it  not  that  there  is 
abundant  evidence  that  a  "profound  ignorance"  of  the 
elementary  principles  of  the  precision  of  measurements  is 
prevalent  among  chemists.  Much  valuable  time  can  be 
saved  and  procedure  simplified  in  many  cases,  if  preliminary 


64       APPARATUS  AND   LABORATORY   MANIPULATION  NOTES 

calculations  of  precision  are  made.  Further,  with  positive 
knowledge  of  the  limit  of  precision  of  all  measurements, 
any  uncertainty  is  reduced  to  a  chance  accident  or  some 
error  inherent  in  the  method. 

It  is  obviously  bad  practice,  for  instance,  to  calibrate  a 
100  cubic  centimeter  flask  on  an  analytical  balance  when 
it  is  practically  impossible  to  read  the  meniscus  to  a  differ- 
ence corresponding  to  less  than  a  centigram  (and  this  dif- 
ference, moreover,  representing  an  error  of  .01  per  cent), 
leaving  out  of  consideration  the  fact  that  with  the  case 
filled  with  moisture,  the  balance  is  for  some  time  quite 
unfit  for  its  necessary  uses,  as  for  weighing  freshly  ignited 
substances,  like  ash.  It  is  also  easily  demonstrated  that 
it  is  absurd  to  weigh  the  normal  weight  of  sugar  to  milli- 
grams, as  recommended  by  eminent  authority. 

The  discussion  of  errors  of  saccharimetric  measure- 
ments given  in  the  previous  chapter  will  illustrate  the 
investigation  of  errors  of  measurement  of  a  polarimetric 
method. 

Notes.  —  Another  vital  point  in  chemical  practice  which 
is  much  neglected,  and  one  not  so  easy  to  acquire  proficiency 
in  as  it  would  seem,  is  that  of  making  complete  and  accu- 
rate record  of  all  the  experimental  data  of  an  analysis. 
Much  valuable  work  is  lost  yearly  through  neglect  of  proper 
recording,  necessitating  a  large  expenditure  of  time  and 
labor  in  repetition.  On  the  other  hand,  the  accurately 
detailed  results  of  the  chemists  of  fifty  years  ago  are  often 
as  valuable  as  the  work  of  to-day,  owing  to  the  complete 
notes  of  data  which  make  it  possible  to  recalculate  the 
results  by  the  constants  which  accord  with  modern  theory 
and  practice. 


APPARATUS  AND   LABORATORY   MANIPULATION  NOTES       65 

In  polarimetry,  owing  to  much  use  of  constant  values  of 
measurement  and  the  mechanical  nature  of  many  of  the 
methods,  there  is  more  temptation  to  take  data  for  granted 
than  in  procedure  where  measurements  peculiar  to  each 
determination  make  record  absolutely  necessary.  The 
laboratory  records  of  polarizations  should,  nevertheless, 
show  exactly  the  value  of  each  datum.  The  tempera- 
ture at  which  the  solutions  are  made  and  polarized,  as 
well  as  the  amount  and  nature  of  the  clarifying  agents 
used,  should  be  recorded  also,  as  these  items  may  well 
be  of  consequence,  especially  in  sugar  analysis,  in  the 
future.  The  test  of  the  value  of  a  set  of  notes  might  be 
put  as  follows,  —  that  at  any  time  in  the  future  they  prove 
complete  enough  to  enable  an  independent  worker  with  a 
knowledge  of  the  literature  of  the  subject  to  duplicate  the 
original  determination  exactly. 

Where  large  numbers  of  determinations  are  made  by  a 
uniform  method,  much  time  can  be  saved  by  the  use  of 
printed  blanks  in  which  appropriate  spaces  are  allotted 
for  data.  Any  important  omission  in  the  record  is  evident 
by  a  glance.  Illustration  is  given  of  such  a  blank  used  by 
students  for  records  of  data  of  a  series  of  twelve  practice 
determinations  in  polarimetry.  In  complicated  calcula- 
tions, such  as  in  the  complete  determination  of  hydrolyzed 
starch  products,  such  blanks,  printed  or  made  by  hekto- 
graph  or  similar  process,  are  particularly  valuable.  The 
computations  are  greatly  simplified  by  printing  the  loga- 
rithmic constants  of  calculations  in  appropriate  tabular 
form,  while  in  addition  there  is  the  important  advantage 
already  mentioned,  that  data,  always  recorded  in  definite 
places,  can  be  read  at  a  glance. 


66       APPARATUS   AND   LABORATORY   MANIPULATION  NOTES 

MASSACHUSETTS  INSTITUTE  OF  TECHNOLOGY 


OPTICAL  ANALYSIS   OF   SUGAR 


No.. 

Date Determination,. 

Instrument Light 

Test. /_ 

Brix /. Brix  (corrected) Sp.  Gr 

w' N- v / 

Test :  Zero  Error : 

Flask    No 

\  Calibration.  _ 


Av. Av Correct  reading. 


Instrument Light 

Test /_ 

Brix /. Brix  (corrected) Sp.  Gr. 

w' N, v L 

Test :  Zero  Error : 


Flask    No... 
Calibration_ 


Av Av -  Correct  reading- 
Result  of  Tests : 

(Signed)... 


APPARATUS  AND  LABORATORY   MANIPULATION  NOTES       6/ 

This  blank  is  introduced  here  merely  as  an  illustration 
of  one  applied  to  a  special  series  of  determinations  many 
of  which  require  two  separate  polarizations  and  some  of 
which,  as  glucose  and  quotient  of  purity  determinations, 
require  Brix  or  density  measurements.  As  suggested,  it 
is  advisable  to  have  data  of  clarification  also.  A  better 
title  would  be  "  Polarimetric  Analysis,"  as  investigation  of 
tartaric  acid  is  also  included. 


NOTES  APPLYING  TO  SPECIAL  INSTRUMENTS 

(To  be  read  in  conjunction  with  the  General  Notes) 
A.    ROTATORY  POLARISCOPES 

The  Laurent  Polariscope.  —  See  that  the  lamp  is  properly 
adjusted  to  give  an  intense  flame.  The  air  valve  (V)  should 
be  regulated  to  give  a  strong  blast,  making  the  blue  cones 
of  the  inner  flame  as  low  as  possible.  The  gauze  basket  (A) 
holding  the  salt  mixture  should  be  parallel  to  the  flame 
cones,  and  be  just  outside  of  them,  in  the  hottest  part  of 
the  flame.  If  care  is  taken  in  this  adjustment,  the  upper 
part  of  the  flame  will  be  a  very  brilliant  yellow  from  the 
incandescent  sodium  vapor.  The  salt  must  be  applied 
every  few  minutes.  The  flame  should  be  about  2  decime- 
ters from  the  end  of  the  polariscope,  the  length  of  an  ordi- 
nary polariscope  tube,  as  the  condensing  lens  (B}  is 
properly  focused  on  the  flame  at  that  distance.  (See 
description  of  improved  lamp  in  previous  chapter.) 

Turn  the  analyzer  by  pinion  G  till  the  scale  (observed  at 
N)  reads  some  degrees  from  zero,  so  as  to  get  a  bright 
illumination,  and  focus  sharply  with  the  eyepiece  (O)  on  the 
luminous  disk  made  by  the  image  of  the  diaphragm  open- 
ing (D)  bisected  by  the  quartz  plate. 

Turn  the  analyzer  to  zero,  and  raise  the  lever  (U)  on  the 
left,  behind  the  scale  disk1  (£7),  till  just  enough  light  passes 

1  In  some  polariscopes  of  the  Laurent  type,  especially  the  German  instru- 
ments, the  adjustment  lever  of  the  polarizer  is  directly  over  the  prism,  its 
movement  being  measured  on  a  graduated  scale. 

68 


NOTES  APPLYING  TO   SPECIAL  INSTRUMENTS 


69 


to  make  a  well-defined  image  in  which  the  shadow  changes 
are  easily  discernible.  This  gives  maximum  sensitiveness. 
Determine  zero  error  at  o  and  180°,  if  the  graduation  of 
the  instrument  admits  of  readings  in  opposite  quadrants. 
If  the  "  eccentricity  "  of  the  scale  is  shown  to  be  less  than  ir 
in  readings  taken  at  different  rotations,  observations  in  the 
opposite  quadrant  can  be  dispensed  with  henceforth.  In 


FIG.  16.  —  LAURENT  POLARISCOPE  AND  SODIUM  LAMP. 

the  larger  instruments,  the  angular-degree  scale  extends 
entirely  around  the  circle,  the  saccharimetric  scale  being 
in  the  upper  half  of  the  circle,  concentric  to  it.  In 
the  smaller  instruments,  the  degree  scale  is  in  one  half  of 
the  circle,  the  saccharimetric  scale  in  the  other.  Study  the 
scales  carefully  till  the  graduation  is  thoroughly  under- 
stood. 

Avoid  turning  the  adjustment  pinion  (F)  on  the  eyepiece 
tube,  as  this  is  intended  for  adjustment  of  the  analyzer 


7O  NOTES  APPLYING  TO   SPECIAL  INSTRUMENTS 

with  the  scale,  and  moves  the  prism  independently  of  the 
scale. 

The  angle  which  the  plane  of  polarization  of  the  polar- 
izer makes  with  that  of  the  Laurent  plate  should  not  be 
too  small,  for  not  only  the  dimness  of  the  light  at  the  end 
point  prevents  distinguishing  with  precision  slight  differ- 
ences of  shade,  but,  inasmuch  as  the  small  amount  of  stray 
blue  rays  which  pass  the  bichromate  plate  are  not  so  com- 
pletely extinguished,  if  at  all,  at  the  end  point,  owing  to 
their  unequal  refrangibility,  these  may  predominate  to  such 
an  extent  when  the  sodium  light  is  too  far  reduced  by 
defective  working  of  the  lamp  or  by  an  excessively  small 
angle  between  the  planes  of  polarization  in  the  two  halves 
of  the  field,  as  to  change  the  "  optical  centre  "  of  the  light 
and  make  an  error  of  some  minutes  in  the  reading.  An 
angle  of  2-4°  to  the  quartz  axis  (which  is  one  half  of 
the  angle  of  tilting  of  the  planes  of  polarization)  is  small 
enough  for  most  accurate  measurements  in  the  work  of  the 
chemical  laboratory.  This  angle  can  be  measured  roughly, 
but  with  sufficient  exactness  for  the  purpose,  by  noting  the 
reading  of  the  scale  at  which  one  half  of  the  field  is  blackest 
when  the  analyzer  is  turned  a  few  degrees  from  zero. 

If  the  lamp  and  instrument  are  properly  adjusted  in  the 
manner  described,  bright  extraneous  light  excluded,  and 
the  direct  rays  of  the  blue  light  of  the  flame  cones  of  the 
lamp  cut  out  of  the  field  by  a  diaphragm,  as  they  are  in 
every  properly  designed  lamp,  no  error  will  be  introduced 
in  readings  certainly  as  great  as  35°  within  the  limit  of 
precision  (V)  of  the  ordinary  laboratory  instrument. 

These  notes  on  the  Laurent  polariscope  apply  also  to 
the  shadow  instruments  using  the  Jellet-Cornu  prism  and 


NOTES  APPLYING  TO   SPECIAL   INSTRUMENTS  71 

the  Lippich  polarizer,  except  what  bears  obviously  on  the 
manipulation  of  the  Laurent  shadow  device  for  changing 
the  light  intensity.  The  Duboscq  rotatometers  usually 
have  an  angle  of  5°  between  the  planes  of  polarization  of 
the  two  halves  of  the  prism,  corresponding  to  2.5°  for  the 
half  angle  measured  as  described  above. 

The  Landolt-Lippich  Polariscope.  —  This  instrument  is 
made  in  a  variety  of  forms,  and  is  especially  designed  for 
exact  physical  measurements.  The  elaborate  measuring 
devices  used  on  the  larger  instruments  for  determining 
optical  rotation  to  .001°  need  not  be  considered  here,  as 
they  are  in  principle  identical  with  those  used  in  precise 
physical  and  astronomical  measurements  by  graduated 
circles.  Some  of  these  instruments  have  the  circle  divided 
into  400  divisions,  instead  of  36O0.1 

1  The  large  Landolt-Lippich  polariscopes  have  the  scale  which  moves  with 
the  analyzer  usually  graduated  directly  to  tenths  of  a  degree.  The  intervals 
less  than  tenths  are  determined  in  thousandths  by  a  "  filar  micrometer."  This 
is  a  device  for  measuring  the  distance  that  the  reference  mark  (shown  in  the 
field  of  the  micrometer  eyepiece  as  a  notch  at  the  side  of  the  graduations) 
lies  from  the  scale  line.  This  is  done  by  moving  two  parallel  cross  hairs  along 
the  scale  by  means  of  a  finely  threaded  screw,  the  distance  traversed  being 
shown  on  a  drum  graduated  into  100  parts,  which  revolves  with  the  screw.  A 
complete  revolution  of  the  drum  (screw)  moves  the  cross  hairs  exactly  one 
tenth  of  a  degree  on  the  scale,  or  the  distance  between  two  scale  lines.  Hence, 
the  reading  of  the  micrometer  drum  when  it  is  set  so  that  a  scale  line  is  ~nid 
way  between  the  cross  hairs  when  taking  the  zero  error  must  be  subtracted 
from  the  reading  of  the  drum  when  it  is  similarly  set  for  determining  the 
desired  rotation  value.  The  reading  of  the  drum  obviously  gives  the  hun- 
dredths  and  thousandths  of  a  degree.  The  readings  are  more  conveniently 
made  if  the  micrometer  is  set  so  that  the  drum  reading  is  zero  when  the  two 
cross  hairs  are  symmetrically  placed  relative  to  the  notch  (most  accurately 
determined  by  first  moving  the  main  scale  till  a  long  graduation  line  lies 
exactly  in  the  notch).  Then  the  readings  of  the  drum  directly  express  the 
interval  in  thousandths  for  each  reading  after  the  manner  of  a  vernier.  This 
adjustment  can  be  made  by  gently  moving  the  drum  on  the  axis  of  the  screw 


72  NOTES    APPLYING   TO   SPECIAL   INSTRUMENTS 

The  illumination  of  the  field  of  the  Lippich  polariscope 
must  be  adjusted  with  great  care,  to  prevent  surface  reflec- 
tion from  the  small  "  half  prism  "  of  the  shadow  device. 
If  the  angle  of  the  polarizer  is  changed  during  a  series  of 
observations,  it  will  be  necessary  to  take  new  zero  readings 
or  bring  the  analyzer  again  into  zero  adjustment  by  means 
of  the  device  provided  for  this  purpose. 

The  Landolt-Lippich  polariscope,  when  used  to  measure 
specific  rotations  for  yellow  light  ("  D  ray  "),  has  the  rays  of 
a  sodium  chloride  lamp  passed  through  a  "  Lippich  sodium- 
light  filter"  consisting  of  two  absorption  cells,  the  first,  I 
decimeter  long,  containing  a  6  per  cent  solution  of  potas- 
sium bichromate,  the  second,  .  1 5  decimeter  long,  containing 
a  solution  of  uranous  sulphate,  U(SO4)2.  This,  according 
to  Landolt,  is  prepared  by  dissolving  5  grams  of  uranyl 
sulphate  in  100  cubic  centimeters  of  water ;  2  grams  of  zinc 
powder  are  added,  and  then  3  cubic  centimeters  of  sul- 
phuric acid,  gradually,  in  three  successive  portions.  Air 
is  excluded  from  the  flask,  which  is  allowed  to  stand  six 
hours  till  the  solution  has  settled.  The  solution  is  then 
filtered  into  the  cell  with  as  little  exposure  to  the  air  as 
practicable.  The  cell  must  contain  as  little  air  as  possible 
and  be  tightly  closed.  It  is  said  that  this  solution  will 
keep  a  month  or  more.  The  bichromate  solution  takes  out 
most  of  the  blue  and  green  rays,  the  dark  green  uranium 

while  the  latter  is  held  stationary  by  the  milled  head,  as  the  drum  is  movable 
on  a  friction  bearing. 

The  micrometers  on  opposite  sides  of  the  scale  disk  can  be  brought  into 
adjustment  to  directly  indicate  the  readings  a  and  a  +  1 80°  respectively,  by 
setting  the  notches  by  a  screw  on  the  end  of  the  micrometer  box  opposite  to 
the  drum.  When  thus  adjusted  the  large  Schmidt  and  Hansch  instruments 
rarely  show  differences  of  .002°  in  opposite  quadrant  readings  at  any  part  of 
the  scale. 


NOTES  APPLYING  TO   SPECIAL   INSTRUMENTS  73 

solution  taking  out  the  rest,  as  well  as  practically  all  of 
the  red  end  of  the  spectrum.  The  resulting  filtered  light 
has,  according  to  Landolt,  a  wave  length  of  .00058932  mil- 
limeter, which  represents  the  wave-length  mean  of  the  two 
D  lines.  In  consequence,  the  rotation  values  are  not 
strictly  comparable  with  those  of  the  Laurent  and  other 
polariscopes  using  sodium  light  filtered  through  a  bichro- 
mate section,  —  being  about  .2  per  cent  greater.1 

The  Wild  Polaristrobometer.  —  This  instrument  is  little 
used  in  this  country,  owing  to  its  unusual  end  point,  not 
readily  distinguishable  by  an  inexperienced  observer,  and 
the  clumsier  arrangement  of  the  apparatus  necessitated  by 
the  rotation  of  the  polarizer  instead  of  the  analyzer.  The 
polariscope  is  capable  of  precise  measurements,  however, 
when  skillfully  manipulated.  As  already  stated,  the  rota- 
tion of  the  polarizer(Z))  is  in  the  reverse  direction  to  the  rota- 
tory effect  of  the  optically  active  substance,  but  in  the  same 
direction  as  the  pinion  (C)  moves  by  which  the  observer 
rotates  the  prism.  The  field,  except  very  near  the  end 
point,  appears  as  a  yellow  disk  covered  with  sharply  de- 
fined, black,  horizontal  lines  like  a  grating.  As  the 
polarizer  is  turned  slowly,  and  the  end  point  is  reached, 
these  lines  disappear,  as  if  rubbed  out  by  an  eraser,  in 
a  broad  band  which  moves  across  the  field.  The  end 

-  In  the  writer's  experience,  the  Landolt  -Lippich  polariscope  gives  much 
more  unreliable  results  than  the  Laurent,  if  a  bichromate  solution  alone  is 
used  as  a  ray  filter.  The  Lippich  polarizer  seems  much  more  sensitive  to  the 
extraneous  rays  present  in  the  sodium  flame  than  the  Laurent,  and  in  conse- 
quence varies  its  end  point  by  several  hundredths  of  a  degree  with  slight 
changes  of  intensity  of  the  flame,  —  under  identical  conditions,  in  fact,  where 
the  Laurent  gives  constant  readings.  With  the  Lippich  ray  filter,  the  Lan- 
dolt-Lippich  readings  are  constant  at  constant  temperature.  Hence,  for 
general  laboratory  purposes,  the  Laurent  polariscope  is  more  suitable. 


74 


NOTES  APPLYING   TO  SPECIAL  INSTRUMENTS 


point  is  taken  as  the  position  of  the  band  in  the  middle 
of  the  field  when  the  unextinguished  lines  of  the  grating 
are  symmetrically  distributed  on  each  side  of  two  cross 
hairs.  The  blank  appearance  at  the  end  point  occurs 
within  a  very  small  angle  of  rotation,  and  consequently 


A.   Eyepiece. 


FIG.  17.  —  WILD  POLARISTROBOMETER. 

B.   Telescope  for  reading  scale  (K).        S.   Mirror  for  illuminating  scale. 


is  so  rapid,  as  the  polarizer  is  turned,  that  the  inexperi- 
enced observer  might  overlook  it  altogether.  The  end 
point  repeats  itself  every  90°,  but  the  appearance  of  the 
field  at  each  end  point  is  not  exactly  the  same,  the  blank 
band  crossing  the  field  at  a  different  angle  in  each  case. 

The  Wild  polaristrobometer  uses  a  salt  flame  without  any 
ray  filter. 


NOTES  APPLYING  TO  SPECIAL  INSTRUMENTS 


75 


B.    QUARTZ-WEDGE  SACCHARIMETERS 

The  Half-shade  Saccharimeter.  —  This  is  the  standard 
instrument  in  use  to-day.  The  general  method  of  focus- 
ing has  already  been  discussed  under  General  Notes. 
The  mean  error  of  this  instrument  when  the  illumination 
is  properly  adjusted  and  the  observer  expert,  is  about  .02 
of  a  scale  division,  but  under  the  usual  conditions  of  using 

JP 


FIG.  18.  —  HALF-SHADE  SACCHARIMETER,  WITH   DIAGRAM  OF  OPTICAL 

PARTS. 

Ft  Et  G.   Quartz  compensator.  K.  Reading  glass  of  scale. 

H.    Adjustment  device  for  rotating  analyzer.     M.  Pinion  for  moving  compensator. 

J.   Eyepiece.  O.  Position  of  Jellet-Cornu  prism. 

N.   Condenser. 

the  saccharimeter  it  is  somewhat  greater.  The  light  should 
fill  the  field  uniformly,  and  not  pass  too  obliquely  through 
the  Jellet-Cornu  prism  (whose  position  in  the  instrument  is 
indicated  at  O\  or  the  surface  of  the  prism  with  its  bisect- 
ing joint  is  too  sharply  defined  (as  well  as  any  dust  that 
may  be  on  its  surface).  The  lamp  and  condensing  lens  of 
the  saccharimeter,  the  latter  adjustable  in  a  sliding  sleeve 
(N\  should  be  arranged  to  pass  the  rays  practically  parallel, 


76  NOTES   APPLYING  TO   SPECIAL   INSTRUMENTS 

or  slightly  convergent.  Landolt  recommends  that  the 
condensing  lens  be  so  placed  relative  to  the  lamp  that 
it  focuses  on  the  analyzer  diaphragm.1  The  field  will 
then  be  always  uniformly  illuminated,  with  the  surface 
of  the  prism  practically  invisible,  the  bisecting  line  show- 
ing very  faintly  at  the  end  point. 

Not  infrequently,  at  the  zero  end  point,  the  field  will  not 
appear  quite  uniform,  one  half  having  a  faint  bluish  tint, 
while  the  other  appears  faintly  brown.  This  is  caused  by 
a  slight  displacement  of  one  of  the  prisms,  and  can  be 
corrected  by  slightly  rotating  the  analyzer  by  means  of 
the  adjustment  provided  for  the  purpose.  In  the  older 
instruments  this  is  done  by  a  key,  which  will  be  found  in 
the  instrument  box,  and  which  fits  a  pinion  (H)  on  the  under 
side  of  the  eyepiece  tube.  This  pinion  turns  a  gearing 
that  revolves  the  analyzer.  The  newer  instruments  have 
a  somewhat  different  device.  On  each  side  of  the  eye- 
piece tube  (J)  there  are  two  steel  screws  with  projecting 
heads.  These  screws  have  conical  points  which  bear  eccen- 
trically on  the  edges  of  two  holes  bored  in  a  rotating  sleeve 
which  carries  the  analyzer.  By  loosening  both  screws, 
and  then  turning  one  or  the  other  down  slightly,  the  effect 
is  to  turn  the  sleeve  in  a  direction  depending  of  course 
on  which  screw  is  turned,  the  rotation  resulting  from 
the  pressure  of  the  coned  point  against  the  side  of  the 
hole  in  the  sleeve.  After  the  analyzer  is  turned  to  correct 
adjustment,  the  screw  which  was  not  used  to  turn  the 
sleeve  is  very  carefully  tightened  till  it  just  bears,  in 
order  to  fix  the  analyzer  in  position.  Extreme  care  should 

1  This  applies  only  to  the  latest  type  of  half-shade  saccharimeters  fitted 
with  the  Lippich  polarizer  and  a  specially  constructed  condenser. 


NOTES  APPLYING  TO  SPECIAL  INSTRUMENTS  77 

be  exercised  in  making  this  adjustment,  as  it  is  one  of  deli- 
cacy. The  method  of  adjusting  is  as  follows:  The  prism 
is  turned,  very  slightly,  and  the  wedge  moved  by  the  pinion 
(M)  till  the  field  is  as  evenly  tinted  as  possible.  If  the 
disparity  of  tint  at  the  end  point  is  diminished,  turn  the 
analyzer  farther  in  the  same  direction  till  no  difference  in 
tint  appears  when  the  wedges  are  adjusted  to  even  shade. 
If  the  disparity  of  tint  increases  on  turning  the  prism,  turn 
in  the  opposite  direction,  each  time  always  adjusting  the 
wedge  for  a  field  of  uniform  shade  (being  also  as  even  a 
tint  as  possible),  independently  of  the  scale  reading. 
After  the  field  is  both  evenly  tinted  and  shaded  at  the 
end  point,  the  scale  may  be  brought  into  adjustment  by 
setting  the  vernier  zero  to  the  scale  zero  by  means  of  the 
key  found  in  the  box.  This  key  fits  on  an  adjustment 
pinion  at  the  left  end  of  the  vernier  scale  (not  shown  in 
cut). 

Many  observers  prefer  to  correct  for  any  disparity  of 
tint  at  the  end  point  by  using  an  absorption  cell  of  potas- 
sium bichromate  solution.  Many  of  the  modern  instru- 
ments are  provided  with  such  an  absorption  cell,  which 
fits  into  the  polarizer  end  of  the  saccharimeter.  This 
cell  absorbs  the  blue  rays,  which  make  the  most  disturb- 
ance, and  gives  an  agreeably  tinted  field  of  uniform  shade 
and  tint  at  the  end  point  even  if  the  prisms  are  slightly 
out  of  adjustment.  This  cell  is  necessary  when  solutions 
of  a  slightly  different  dispersive  power  from  quartz  are 
polarized,  commercial  "  glucose,"  for  instance.  In  fact,  if 
white  light  is  used,  there  will  be  a  slight  disparity  of  tint 
at  high  rotations,  even  with  cane-sugar  solutions,  as  the 
dispersive  powers  of  cane  sugar  and  quartz  differ  some- 


78  NOTES  APPLYING  TO  SPECIAL  INSTRUMENTS 

what  at  the  blue  end  of  the  spectrum.  A  piece  of  brown 
(carbon)  tinted  glass  is  a  very  good  substitute  for  the  bi- 
chromate cell,  although  it  does  not  cut  off  the  blue  rays 
quite  as  effectively.  It  may  be  well  to  note  again  the 
considerable  error  caused  by  varying  temperature.  For 
accurate  work  it  is  necessary  that  the  saccharimeter  be 
exposed  for  at  least  an  hour  to  a  temperature  practically 
uniform  with  that  at  which  the  readings  are  made.  The 
exact  graduation  should  be  established  by  means  of  stand- 
ard quartz  plates  of  known  values,  since  instruments  are 
graduated  by  at  least  two  systems,  as  has  already  been 
noted,  one  based  on  the  Mohr  cubic  centimeter  of  17.5°, 
—  the  original  Ventzke  and  established  commercial  stand- 
ard ;  the  other,  the  official  standard  of  the  United  States 
Custom  House,  based  on  true-cubic-centimeter  volumes.1 

The  Triple-shade  Saccharimeter.  —  This  instrument  dif- 
fers from  the  standard  commercial  saccharimeter  only  in 
the  end-point  device,  which  is  the  Lippich  triple-prism 
polarizer,  the  essentials  of  which  are  a  large  Nicol  prism, 
and  two  smaller  Nicols  placed  close  to  the  large  Nicol, 
between  it  and  the  analyzer.  These  two  smaller  "half 
prisms,"  as  they  are  called,  have  their  vibration  planes 
parallel  to  each  other,  but  at  a  slight  angle  to  that  of  the 
larger  Nicol.  The  light  from  this  polarizer  passes  through 
the  circular  opening  of  a  diaphragm  in  such  a  way,  and 

1  Apparently  some  saccharimeters,  especially  the  later  ones,  are  graduated 
to  give  exact  percentages  of  cane  sugar  at  all  concentrations.  Such  scales  are 
not  strictly  proportional  to  the  quartz  rotation  values,  as  the  specific  rotation 
of  sugar  increases  slightly  with  diminishing  concentration.  Hence  the  sur- 
face of  the  "  wedges  "  must  be  curved  or  the  divisions  vary  in  size.  Many 
of  the  newer  instruments,  graduated  for  true  cubic  centimeter  flasks,  when 
compared  with  the  Ventzke  graduation,  show  at  the  100  point  the  ratio, 
I. ooooo:  1.00234,  Dut  lu  tne  middle  of  the  scale,  i.oooo  :  1.0033. 


NOTES  APPLYING  TO   SPECIAL  INSTRUMENTS 


79 


FIG.  19. 


the  half  prisms  are  so  arranged,  that  the  field  is  trisected 
vertically  by  the  edges  of  the  two  half  prisms.  The  dia- 
gram shows  the  position  of  the  prisms  relative  to  the  field 
of  the  instrument.  The  circle  repre- 
sents the  field  defined  by  the  diaphragm 
opening;  A  and  B  show  the  positions 
of  the  half  prisms  and  C  that  of  the 
large  Nicol.  Then,  if  the  vibration 
planes  of  the  two  half  prisms  are 
taken  parallel  to  aa1  and  bV ',  and  cc^ 
inclined  at  a  small  angle  to  aaf  or 
bV ,  represents  the  vibration  plane  of  the  large  Nicol  C, 
the  field  will  be  equally  illuminated  when  the  vibration 
plane  of  the  analyzer  is  at  right  angles  to  a  line  bisecting 
the  angle  made  by  the  vibration  plane  of  the  Nicol  C 
and  that  of  either  half  prism  A  or  B.  The  diagram  in 
plan  shows  the  position  of  the  prisms  relative  to  the  light 

passing  through  the  instru- 
ment  along  its  axis  in  the 
direction  shown  by  the 
arrow  through  the  lens  L, 
the  diaphragm  being  at  D. 
It  will  be  noticed  that  the 
half  prisms  are  slightly  canted  longitudinally.  This  is  to 
insure  a  sharp  focus  on  the  edge  of  the  prism,  so  that  its 
image  at  the  end  point  will  be  a  faint  hair  line. 

Obviously,  the  light  effect  in  the  two  side  sections  of 
the  field  is  the  same  when  the  plane  of  the  light  is  rotated, 
the  contrast  being  between  these  and  the  central  section, 
instead  of  in  the  halves  of  the  field  as  in  the  half-shade 
saccharimeter.  Owing  to  the  agreeable  effect  of  the 


FIG.  20. 


80  NOTES   APPLYING  TO   SPECIAL  INSTRUMENTS 

triple-shade  field,  this  instrument  has  become  very  popu- 
lar. However,  on  account  of  the  complication  and  deli- 
cacy of  the  prism  combination,  it  is  much  more  liable  to 
get  out  of  adjustment,  the  exact  parallelism  of  the  two 
half  prisms  being  difficult  to  maintain.  It  is  therefore 
doubtful  whether,  under  the  ordinary  conditions  of  its  use 
in  the  sugar  laboratory,  it  really  gives  readings  of  greater 
precision  than  those  of  the  half-shade  saccharimeter,  espe- 
cially when  the  latter  has  its  illuminating  apparatus  ad- 
justed to  give  the  best  field  for  accurate  reading. 

Variations  in  temperature  will  apparently  affect  the 
half -prism  adjustment,  as  well  as  any  shock  or  jar  to  the 
instrument.  The  result  is  that  the  field  at  the  end  point 
will  not  be  perfectly  evenly  illuminated,  but  one  or  the 
other  of  the  side  sections  will  show  a  faint  shading. 
There  will  be,  in  consequence,  two  end  points,  depending 
on  which  side  of  the  field  is  evenly  illuminated  with  the 
central  section.  Usually  this  disparity  is  less  than  .1  of 
a  scale  division,  but  the  precision  of  the  instrument  is  low- 
ered by  that  amount,  unless  the  observer  goes  through  the 
tedious  process  of  taking  the  average  of  the  readings  by 
each  end  point,  and  thereby  halves  his  error.  This  defect, 
however,  is  an  annoying  one  and  of  course  does  away  with 
any  superiority  of  precision  over  the  simpler  half-shade 
type. 

If  the  theory  of  the  Lippich  polarizer  is  thoroughly 
understood,  any  one  experienced  in  working  with  delicate 
instruments  can  adjust  the  half  prisms  to  parallelism  in  the 
following  manner  :  Remove  the  screws  in  the  metal  sheath 
of  the  enlarged  part  of  the  tube  containing  the  polarizer. 
Take  the  sheath  off,  which  will  expose  the  half  prisms  in 


NOTES  APPLYING  TO   SPECIAL   INSTRUMENTS 


8l 


their  brass  mountings.  Both  of  these  mountings  can  be 
rotated  through  a  small  angle,  and  one  is  provided  with 
coned-screw  adjustments  for  making  a  very  small  rotation, 
exactly  as  described  in  the  Notes  on  the  Half-shade  Sac- 
charimeter.  If  the  screws  of  the  slotted  guides  holding 


FIG.  21.  —  DOUBLE-WEDGE,  TRIPLE-SHADE  SACCHARIMETER  WITH  DIAGRAM 
OF  OPTICAL  PARTS. 


t,  N~z.  Half  prisms. 


Polarizer. 


the  mounting  of  the  prism  to  be  rotated  are  loosened,  then 
the  delicate  adjustment  to  parallelism  can  be  made  with  the 
coned  screws,  in  a  similar  way  to  that  already  described. 
When  the  field  shows  perfectly  uniform  illumination  at  the 
end  point,  the  screws  in  the  guide  slots  are  gently  tight- 
ened to  hold  the  mounting  in  position.  Considerable  skill 
and  patience  are  required  to  make  this  adjustment.  Great 


82  NOTES  APPLYING  TO   SPECIAL  INSTRUMENTS 

care  should  be  taken  to  move  only  those  screws  which 
have  to  do  with  this  adjustment,  as  there  are  other  screws 
which  rotate  the  prism  longitudinally. 

The  newer  triple-shade  as  well  as  half-shade  saccha- 
rimeters  have  the  scale  illuminated  by  means  of  a  small 
mirror  over  the  scale,  which  throws  the  light  of  the  main 
lamp  of  the  saccharimeter  down  through  a  ground  glass 
upon  the  scale.  This  obviates  the  necessity  of  a  separate 
scale  light.  If  the  saccharimeter  is  screened  from  the 
light  by  a  partition,  or  placed  in  a  hood,  care  should  be 
taken  to  have  the  hole  through  which  the  light  passes 
large  enough  to  allow  a  diagonal  ray  to  the  mirror.  A 
mirror  of  any  kind  fastened  to  the  top  of  the  hood  by 
means  of  a  stiff  bent  wire,  when  properly  placed,  works 
well  with  the  older  form  of  scale  apparatus.  A  cheap, 
silvered-glass  concave  reflector,  such  as  used  with  an  ordi- 
nary kerosene  lamp,  works  excellently. 

The  Soleil-Ventzke-Scheibler  Transition-tint  Saccharime- 
ter. —  This  instrument,  which  was  the  standard  commer- 
cial saccharimeter  less  than  fifteen  years  ago,  is  now 
almost  completely  replaced  by  the  half-shade  type.  It 
takes  considerable  practice  to  get  high  precision  in  obser- 
vations with  a  transition-tint  saccharimeter,  but  an  expert 
with  a  good  eye  for  color  can  read  the  tint  transition  as 
accurately  as  the  half-shade  end  point,  unless  possibly  in 
the  case  of  very  highly  colored  solutions,  such  as  low- 
grade  molasses.  The  errors  of  reading  such  solutions  are, 
however,  much  less  than  others  peculiar  to  polarizing  such 
products,  to  be  discussed  later.  The  normal  weight  used 
with  this  instrument  (26.048  grams)  and  in  fact  all  the 
working  parts,  except  those  which  have  to  do  with  the 


NOTES  APPLYING  TO  SPECIAL  INSTRUMENTS 


special  end-point  device,  are  identical  with  those  of  the  half- 
shade  saccharimeter. 

The  method  of  using  this  instrument  is  as  follows : 
Focus  the  eyepiece  (_/)  on  the  transition-tint  plate,  which 
will  appear  as  a  party-colored  disk  of  two  contrasting 
colors,  each  occupying  one  half  of  the  field  on  each  side  of 
a  central  vertical  line.  Turn  the  scale  to  zero,  or  till  both 
halves  of  the  field  are  of  the  same  tint ;  then  turn  the  button 


F  E 


E 


FlG.    22. —  SOLEIL-VENTZKE-SCHEIBLER    TRANSITION -TINT    SACCHARIMETER. 


A.  Shows  position  of  Nicol  of  tint 

producer. 

B.  Position  of  quartz  plate  of  tint 

producer. 

C.  Position  of  polarizer. 

D.  Position  of  transition-tint  plate. 


Fy  £,  G.  Quartz-wedge  compensator. 

H.  Adjustment  device  of  analyzer. 

y.  Eyepiece. 

K.  Reading-glass  of  scale. 

L.  Pinion  for  setting  sensitive-tint  producer. 

M.  Pinion  for  moving  wedge. 


on  the  end  of  the  long  rod  (Z)  at  the  right  of  the  eyepiece, 
which  turns  the  Nicol  of  the  "  sensitive-tint  producer,"  till 
a  suitable  tint  is  produced  in  the  field  for  a  background 
against  which  the  eye  can  most  readily  distinguish  the 
delicate  rose  tint  which  appears  in  one  or  the  other  half  of 
the  field  when  the  wedge  is  almost  at  the  end-point  posi- 
tion. The  tint  chosen  varies  with  different  observers.  It 
is  always  a  very  pale  one,  flesh  or  pearl,  practically  white. 
The  end  point  shows  both  halves  of  the  field  evenly  tinted 


84  NOTES   APPLYING  TO   SPECIAL   INSTRUMENTS 

with  this  sensitive  color,  but  at  the  slightest  turn  of  the 
wedge  pinion  a  pale  rose  flush  will  appear  in  one  half  of 
field  or  the  other.  The  light  from  the  lamp  should  be 
soft  and  diffused,  not  too  bright.  In  taking  zero  observa- 
tions, many  place  a  tube  full  of  water  in  the  instrument  to 
soften  the  light.  As  the  eye  becomes  fatigued  quickly, 
and  loses  its  maximum  sensitiveness  for  distinguishing 
slight  changes  in  tint  in  a  few  moments,  rapid  readings 
should  be  made.  All  glaring  outside  light,  especially  if 
colored,  should  be  excluded,  the  observer  being  in  com- 
parative darkness.  When  a  colored  solution  is  placed  in 
the  instrument,  the  sensitive  tint  must  be  again  adjusted 
till  the  color  is  obtained  which  proves  most  sensitive  for 
observing  the  end-point  transition.  With  highly  colored 
solutions  of  molasses  or  molasses  sugars,  the  transition 
change  appears  as  a  shadow,  owing  to  the  practically 
complete  absorption  of  the  tint  by  the  deep  brown-red  of 
the  caramel  substance  of  the  molasses. 

Occasionally,  especially  in  an  old  instrument,  the  prisms 
become  displaced  sufficiently  to  affect  the  sensitiveness  of 
the  readings,  the  field  not  appearing  perfectly  uniform  at 
the  end  point.  The  quickest  and  surest  way  to  bring  the 
instrument  in  adjustment  is  to  remove  the  quartz-wedge 
compensation  entirely,  and  then  adjust  the  analyzer  till  the 
field  is  evenly  tinted.  As  in  the  adjustment  of  the  analyzer 
in  the  half -shade  saccharimeter,  this  is  done  by  means  of  a 
key  which  turns  a  pinion  (//")  on  the  under  side  of  the  eye- 
piece tube.  To  remove  the  compensator,  slip  out  the 
movable  wedge  (E\  unscrew  the  brass  plate  carrying  the 
fixed  wedge  (F)  and  the  vernier  scale,  and  finally,  remove 
the  left-rotating  quartz  section  which  is  the  last  optical 


NOTES   APPLYING  TO   SPECIAL  INSTRUMENTS  85 

part  on  this  end  of  the  instrument  going  toward  the 
polarizer.  This  is  done  by  unscrewing  the  brass  ring  of 
the  mounting  (G)  from  the  trough  side. 

The  Soleil-Duboscq  Transition-tint  Saccharimeter.  - 
This  instrument  has  been  entirely  superseded  in  commer- 
cial work  by  the  improved  modern  types  of  quartz-wedge 
saccharimeters.  The  wedges  of  the  Duboscq  instruments 
are  well  made,  however,  and  in  the  hands  of  a  skillful 
worker  it  is  a  precise  instrument  to  at  least  .2  of  a  divi- 
sion, an  accuracy  sufficient  for  many  laboratory  measure- 
ments. A  conscientious  and  painstaking  observer  with  a 
good  eye  for  color  can  make  efficient  use  of  such  a  saccha- 
rimeter,  since  its  deficiencies  are  largely  those  of  incon- 
venience and  difficulty  of  manipulation,  and  these  can  be 
supplemented  by  exercising  a  correspondingly  greater  skill 
in  working  with  the  instrument.  The  young  chemist  is 
apt  to  condemn  too  hastily  any  laboratory  instrument 
which  is  not  of  modern  type,  when  a  little  practice  and  a 
study  of  the  nature  and  magnitude  of  the  errors  of  analy- 
sis would  show  that  such  apparatus  fulfills  all  the  require- 
ments of  the  work  at  hand.  Of  course,  in  the  case  of  large 
commercial  laboratories,  where  accuracy  with  speed  and 
uniform  trade  methods  are  the  leading  considerations,  the 
standard  modern  saccharimeter  is  indispensable. 

The  fundamental  principles  of  the  working  of  the  Du- 
boscq-Soleil  saccharimeter  are  identical  with  those  of  the 
Soleil-Ventzke,  but  the  details  of  the  apparatus  are  con- 
siderably different.  Both  wedges  of  the  compensator  are 
moved  by  the  pinion  past  each  other,  instead  of  one  being 
fixed  as  in  the  modern  instrument.  The  scale,  which  is 
graduated  for  a  normal  weight  of  16.35  grams,  or  what 


86  NOTES   APPLYING  TO   SPECIAL   INSTRUMENTS 

was  taken  as  the  equivalent  of  the  rotation  of  a  millimeter 
section  of  quartz,  has  no  vernier,  and  reads  from  right  to 
left,  the  fractions  being  estimated  by  aid  of  a  hand  magni- 
fier. The  sensitive-tint  producer  is  in  the  eyepiece,1  which 
latter  in  consequence  moves  in  a  slotted  guide  to  avoid  any 
disturbance  of  the  tint  in  focussing.  The  Nicol  for  pro- 
ducing the  sensitive  tint  can  be  rotated  through  a  half 
circle  by  means  of  a  milled  ring  on  the  eyepiece  tube. 

A  trough  can  be  made  very  cheaply  which  will  fit  into 
the  instrument  and  so  allow  the  use  of  the  more  convenient 
modern  tubes,  which  are  of  smaller  diameter. 

Double-wedge  Saccharimeters.  —  In  these  instruments, 
the  scales  read  to  the  left,  the  figures  of  the  "  working 
wedge "  scale  being  in  black  and  those  of  the  "  control 
wedge  "  in  red.  The  pinion  head  of  the  "  control  wedge  " 
is  also  of  a  different  color  from  that  of  the  "working 
wedge,"  and  placed  at  a  different  level  to  avoid  confusion. 
Double-wedge  scales  have  read  from  right  to  left  in  all 
saccharimeters  of  this  type  which  have  come  under  the 
author's  notice.  The  scales  do  not  have  minus  gradua- 
tions, as  left-rotating  solutions  can  be  read  by  using  the 
control  wedge  as  the  working  wedge.  When  a  double- 
wedge  saccharimeter  is  in  adjustment,  and  no  optically 
active  substance  is  in  the  instrument,  the  end  point  is 
always  given  when  the  wedges  are  so  adjusted  that  both 
scales  read  alike,  independently  of  the  numerical  value  of 
the  reading.  (See  Figures  10  and  21.) 

1  It  is  interesting  that  the  illustration  of  a  saccharimeter  in  Clerget's  original 
article  on  sugar-testing,  written  in  1849  (Ann.  Chim.  Phys.  26  (3),  175), 
shows  an  arrangement  of  tint  producer  identical  with  the  modern  instrument 
of  Scheibler. 


POLARIZATION  OF  CANE  SUGAR.— GENERAL 
COMMERCIAL  METHODS 

Sampling.  —  In  most  commercial  analyses  the  sugar  is 
determined  as  a  per  cent  by  weight  of  the  original  product 
as  it  is  bought  and  sold  in  the  market.  The  sample  which 
the  chemist  polarizes  must  be  strictly  representative  of  the 
total  lot  of  sugar,  which  may  amount  to  several  thousand 
tons.  The  sampling  of  such  large  lots  of  sugar  entails 
much  labor,  and  in  the  case  of  raw  sugars  is  usually  done 
by  men  specially  trained  for  this  work.  Great  care  has  to 
be  exercised,  as  it  is  by  no  means  easy  to  get  a  representa- 
tive sample.  Not  only  is  sugar  bought  and  sold  on  its 
percentage  value,  but  the  government  assesses  import 
duties  based  on  the  polarization,  which  may  amount  to 
from  30  to  50  per  cent  of  the  total  value  of  the  cargo. 
Raw  sugar  reaches  the  market  in  diverse  forms  of  package. 
The  old-fashioned  "open  kettle"  or  muscovado  sugar, 
some  of  which  is  still  shipped,  comes  in  hogsheads  of 
from  1500  to  1650  pounds.  The  modern  West  Indian 
sugar  houses  usually  ship  in  burlap  bags  of  300  pounds. 
The  Hawaiian  sugar  comes  in  125-pound  bags.  The 
Javan  sugar  is  packed  in  cylindrical  bamboo  crates,  hold- 
ing about  700  pounds.  Some  sugar  is  packed  in  wooden 
boxes,  and  the  primitive  palm  sugars  of  the  East  come  in 
bamboo  "mats." 

The  sampling  of  raw  sugars  is  especially  difficult  be- 
cause the  product  contains  considerable  moisture  from  the 

87 


88  POLARIZATION  OF  CANE   SUGAR 

molasses,  which  is  retained  by  the  spongy  mass  of  crystals, 
the  amount  varying  greatly  with  the  quality  of  the  sugar. 
This  molasses  tends  to  drain  from  the  upper  layers  of  the 
package  and  collect  at  the  bottom.  Most  sugars  exposed 
to  the  air  rapidly  lose  their  moisture.  In  consequence, 
sugar  samples  taken  from  different  parts  of  a  package 
may  differ  appreciably  in  polarization.  The  method  of 
sampling  found  most  satisfactory  in  practice  is  to  thrust 
a  long  metal  tube,  known  as  a  "  trier,"  through  the  whole 
bulk  of  the  package,  in  a  line  extending  diagonally  from 
the  top  of  one  side  to  the  bottom  of  the  other.1  By  rotat- 
ing the  trier,  it  is  filled  with  sugar  its  entire  length. 

In  this  way  each  package,  or  a  certain  percentage  of 
the  packages,  of  the  cargo  is  sampled,  and  the  sugar  from 
the  sampling  transferred  as  quickly  as  possible  to  a  cov- 
ered can  or  metallic  box  to  prevent  drying.  After  a 
thorough  mixture  of  this  large  sample,  small  samples  are 
taken  from  it  which  are  put  into  tin  boxes  holding  half  a 
pound  or  so.  These  are  tightly  covered  and  often  sealed 
by  dipping  the  box  in  paraffin.  It  is  in  this  form  that  the 
samples  go  to  the  laboratory.  Molasses  or  sirups  are  sam- 
pled by  running  a  stick  into  the  bunghole  of  the  barrel  or 
hogshead  and  draining  off  the  adhering  liquid  into  a  bottle. 

Method  of  Polarizing.  — The  commercial  method  of  polar- 
izing is  as  follows :  Mix  the  sample  thoroughly,  breaking 
up  all  lumps.  This  is  best  done  by  pouring  out  the  con- 
tents of  the  box  upon  a  sheet  of  ordinary  brown  calendered 
wrapping  paper,  or,  better,  a  sheet  of  plate  glass.  Weigh 
out  the  normal  weight  of  sample  in  the  tared  German- 

1  Bags  and  baskets  of  "  centrifugal "  sugars  are  sampled  by  driving  the  trier 
in  at  the  side  so  as  to  sample  the  central  contents. 


POLARIZATION  OF  CANE  SUGAR  89 

silver  dish  provided  for  the  purpose,  weighing  to  .005 
gram.  The  preparation  of  the  sample  and  the  weighing 
should  be  done  as  quickly  as  possible  and  the  remainder 
of  the  sample  returned  to  the  covered  box  at  once  to  avoid 
change  from  evaporation.  Pour  about  50  cubic  centime- 
ters of  water,  at  room  temperature,  into  the  dish,  and  stir 
up  the  crystals  from  the  bottom  with  the  little  metallic 
pestle  provided  for  the  purpose.  It  is  usually  not  neces- 
sary to  grind  the  sample  with  the  pestle  in  dissolving,  as 
this  does  not  materially  assist  solution,1  and  wears  the  dish. 
Pour  off  the  solution  into  a  loo-cubic-centimeter  graduated 
flask,  taking  especial  care  not  to  pour  out  any  undissolved 
sugar.  Very  fine  crystals  are  often  carried  into  the  flask 
if  care  is  not  taken  to  prevent  it,  and,  settling  to  the  bot- 
tom, remain  undissolved.  Add  a  little  water  to  dissolve  the 
rest  of  the  sugar  in  the  dish.  There  is  usually  left  a  slight 
residue  of  insoluble  matter,  sand  or  dirt. 

As  aqueous  solutions  of  raw  sugars  are  practically  opaque 
from  the  presence  of  albuminoid  and  other  vegetable 
extractive  matter  in  a  colloidal  state,  it  is  necessary  to  use 
some  precipitant  to  clarify  the  solution  in  order  to  get  it 
into  a  suitable  condition  to  polarize.  A  solution  of  basic 
lead  acetate  of  a  density  of  1.25  is  the  clarifier  almost  uni- 
versally used. 

After  the  solution  has  been  entirely  washed  into  the 

1  Another  method  of  solution  is  to  wash  the  sugar  through  a  wide-mouthed 
funnel  directly  from  the  dish  into  the  flask  by  means  of  a  wash  bottle  or  other 
convenient  jet  apparatus.  The  flask  is  filled  about  three  quarters  full,  and  is 
shaken  till  the  sugar  is  dissolved.  This  is  the  official  German  method.  With 
a  large  number  of  samples  it  is  quicker,  as  the  flasks  can  be  placed  in  a 
shaking  machine  and  all  shaken  at  once.  With  a  few  it  is  slower,  but  it  has 
the  advantage  that  the  weighing  dishes  are  not  worn  by  any  grinding. 


90  POLARIZATION  OF  CANE  SUGAR 

flask,  allow  it  to  stand  a  few  minutes  so  that  any  solution 
in  the  neck  may  drain  off,  add  2  cubic  centimeters  of  basic 
lead  acetate  solution,  and  make  up  to  the  graduation  mark 
with  water.  If  foam  prevents  the  reading  of  the  meniscus, 
add  a  drop  of  ether,  or  better,  spray  a  little  ether  into  the 
flask  with  an  atomizer.  This  will  immediately  dissipate  the 
foam.  Shake  the  solution  and  filter  through  a  dry  filter  into 
a  (dry)  cylinder,  rejecting  the  first  few  drops.  Cover  the 
funnel  with  a  watch-glass  to  avoid  evaporation. 

The  amount  of  lead  acetate  solution  necessary  for  clari- 
fication varies  with  the  nature  of  the  sugar  polarized.1  No 
exact  rule  can  be  given.  Use  as  little  as  possible.  If  too 
little  lead  solution  is  used,  the  clarification  is  incomplete ; 
if  too  much,  the  solution  soon  clouds  after  filtering  from  the 
formation  of  basic  salts  or  carbonate.  If  the  right  amount 
of  lead  has  been  added,  and  thoroughly  mixed  through  the 
solution,  after  a  few  minutes  a  distinct  coagulation  will  be 
noticed,  the  particles  gradually  settling  out  and  leaving  at 
the  surface  a  comparatively  clear  solution.  The  addition  of 
about  2  cubic  centimeters  of  " alumina  mixture"  —a  solu- 
tion of  alum  almost  completely  precipitated  by  ammonia 
so  as  to  be  practically  a  creamy  mixture  of  aluminum 
hydrate  in  ammonium  sulphate  solution  —  assists  clarifica- 
tion and  removes  any  excess  of  soluble  lead.2  A  5  Per 

1  Another   method   of  clarification  has  been  proposed  very  recently  by 
Home  (/.  Am.  Chem.  Soc.,  XXVI,  186),  which  is  designed  to  obviate  the 
effect  of  the  volume  of  the  precipitate  on  the  concentration.     In  this  method 
the  solution  is  made  up  to   100  cubic  centimeters  previously  to   clarifying. 
A  sufficient  quantity  of  basic  lead  acetate  in  powdered  form  is  added  and  the 
solution  filtered. 

2  This  is  important  if  the  solution  is  to  be  inverted  by  the  Clerget  method 
(described  in  the  next  chapter),  to  prevent  removal  of  hydrochloric  acid  by 
the  lead  in  the  filtrate, 


POLARIZATION   OF   CANE   SUGAR  9 1 

cent  solution  of  common  salt  is  also  excellent  for  the  latter 
purpose. 

Dark  solutions,  as  from  molasses,  sometimes  require 
either  diluting  or  the  use  of  the  i -decimeter  tube.1  Occa- 
sionally the  solution  is  decolorized  by  placing  a  gram  or  so 
of  prepared  bone  black  in  the  dry  filter.  Owing  to  the 
initial  absorption  of  sugar  by  the  black,  the  first  30  cubic 
centimeters  of  the  filtrate  should  be  rejected.  Decoloriza- 
tion  by  bone  black  should  only  be  used  as  a  last  resort. 
Highly  refined  sugars,  such  as  granulated,  usually  need  no 
clarification  other  than  simple  filtration.  Often,  when  a 
precipitant  is  necessary,  the  alumina  mixture  alone  suffices. 

Polariscope  Tubes.  —  In  filling  tubes  avoid  air  bubbles. 
These  obviously  cut  off  the  field  and  impair  the  definition 
unless  very  small,  when  they  need  not  be  considered. 
Rinse  the  tube  twice  with  the  solution  before  filling. 

Before  placing  a  tube  in  the  instrument  wipe  carefully, 
and  see  that  the  outside  of  the  cover  glasses  is  clean  and 
free  from  moisture.  If  objects  cannot  be  seen  clearly  and 
without  distortion  when  looking  through  the  tube,  it  is  use- 
less to  try  to  make  a  polariscope  reading,  and  it  should  be 
refilled.  If  the  tube  is  handled  much,  the  heat  of  the  hand 
will  temporarily  disturb  the  solution,  causing  a  turbidity 
which  will  soon  clear. 

In  placing  caps  on  polariscope  tubes,  note  that  the  number 

1  Sawyer  (y.  Am.  Chem.  Soc.,  27  (July))  shows  by  many  experimental  data 
that  it  is  better  to  polarize  low-grade  molasses  in  fifth  normal  solution 
(26.048  grams  in  500  cubic  centimeters).  Aside  from  the  greater  con- 
venience in  making  up  the  solution  and  the  saving  of  eyesight  in  reading  the 
lighter  colored  filtrate,  less  than  one  half  as  much  basic  lead  acetate  is  nec- 
essary ;  hence,  the  errors  due  to  clarification  are  correspondingly  decreased, 
as  is  the  effect  of  the  bulk  of  the  precipitate  in  the  larger  volume  of  solution. 
These  advantages  more  than  compensate  for  the  increased  errors  of  reading. 


92  POLARIZATION   OF   CANE   SUGAR 

or  symbol  on  the  cap  corresponds  with  that  on  the  tube. 
This  will  prevent  jamming  or  sticking  of  the  caps.  The 
friction  caps  of  the  Landolt  tubes  should  be  firmly  seated 
by  pressing  them  on  with  a  rotary  motion.  Screw  caps 
should  be  screwed  on  firmly  and  then  very  slightly  slack- 
ened, so  that  the  pressure  on  the  cover  glass  is  from  the 
expansion  of  the  soft  rubber  washer  which  is  a  necessary 
fitting  in  the  cap  of  both  types  of  tube.  See  that  this 
washer  is  always  in  the  cap. 

After  using,  all  apparatus  that  has  been  in  contact  with 
solutions  should  be  thoroughly  washed  with  running  water 
and  placed  in  a  rack  to  dry  (not  wiped).  This  will  insure 
a  constant  supply  of  clean  dry  apparatus.  Take  care  to 
wash  the  brasswork  at  the  ends  of  the  tubes,  especially 
the  Landolt,  or  the  caps  will  stick.  After  washing,  leave 
cover  glasses  out,  but  place  caps  on  the  ends  of  the  tubes 
so  as  to  protect  the  ground  surfaces  from  being  chipped 
by  any  chance  knock.  The  lead  used  for  clarifying  in 
sugar  solutions  gradually  clouds  glassware.  Remove  by 
occasional  washing  in  hydrochloric  acid.  If  cover  glasses 
stick  in  the  caps,  force  them  out  with  a  clean  stick  of  wood ; 
do  not  use  metal  or  glass.  Care  should  be  exercised  to 
avoid  scratching  the  cover  glasses  in  any  way.  Scratched 
cover  glasses  should  not  be  used.  Glass  polariscope  tubes 
are  preferable  to  metal  ones  from  their  greater  cleanliness 
and  because  they  are  less  affected  by  temperature  changes. 

The  brass  mountings  at  the  ends  of  glass  tubes  should 
always  be  examined  before  using  the  tubes,  as  they  occa- 
sionally work  loose  and  become  pushed  out  so  that  the 
cover  glasses  bear  on  the  brass  and  not  on  the  ground-glass 
ends  of  the  tube  as  they  should.  By  gently  heating  the  end 


POLARIZATION   OF   CANE   SUGAR 


93 


of  the  tube  till  the  resinous  cement  which  holds  the  mount- 
ing melts,  the  brass  collar  can  be  pushed  back  till  the  ground 
end  of  the  tube  is  just  exposed,  and  allowed  to  cool  in  this 
position  till  the  cement  hardens.  A  good  quality  of  seal- 
ing wax  makes  a  good  cement,  or  better,  especially  in  warm 
climates,  a  mixture  of  litharge  and  glycerine,  which  rapidly 
hardens  when  gently  heated. 


FIG.  23.  —  WATER- JACKETED  TUBE  FOR  POLARIZING  AT  CONSTANT 
TEMPERATURE. 

A,  Tubulus  for  thermometer.  D.    Rubber  stopper. 

B,  C.   Water  jacket  connections.  E.   Thermometer. 

F.   Air  vent  for  equalizing  pressure  on  liquid  in  tube. 

Tubes  for  ordinary  laboratory  instruments  are  usviall) 
made  of  three  lengths,  i,  2,  and  4  decimeters.  The  stand 
ard  tube  for  commercial  work  is  2  decimeters  in  length. 
Tubes  used  for  inversion  readings,  to  be  mentioned  later, 
are  2.2  decimeters  long  and  provided  with  a  tubulus  for 
holding  sufficient  solution  in  which  to  immerse  a  ther- 
mometer bulb  for  taking  the  temperature  of  the  solution  in 
the  tube  during  readings.  Preferably  such  tubes  are  sur- 


94  POLARIZATION   OF  CANE  SUGAR 

rounded  by  a  circulating- water  jacket  for  maintaining  con- 
stant temperature. 

Certain  forms  of  tubes  have  been  designed  with  an 
enlarged  chamber  to  trap  any  air  bubbles  which  might 
accidentally  be  introduced  into  the  tube,  and  keep  them  out 
of  the  optical  field  of  the  saccharimeter.  With  ordinary 
care  in  manipulation  no  such  devices  are  necessary. 

Pellet  has  devised  a  "  continuous  diffusion  "  tube  which 
by  means  of  tubulature  connections  can  be  filled  without 
removing  from  the  saccharimeter.  This  apparatus  is  very 
useful  where  a  large  number  of  polarizations  are  to  be 
made  quickly,  as  in  valuing  beets. 

Of  course  if  /  is  not  2,  v  not  100,  or  the  weight  of  sample 
taken  (wf)  not  the  normal  weight  (/V),  the  reading  of  the 
saccharimeter  will  not  express  directly  the  per  cent  of 
sugar.  If,  for  instance,  the  weight  of  sample  is  other  than 
the  normal  weight,  the  percentage  will  be  given  by  the 

N 

following  equation,  P  =  R— 7,  where  R  is  the  reading,  and 

P  is  the  per  cent  required. 

Manipulation  of  the  Schmidt  and  Hansch  Control  Tube. 
—  The  principles  on  which  the  use  of  this  instrument 
depends  in  its  application  to  the  calibration  of  saccha- 
rimeters  have  already  been  explained.  The  method  of 
manipulation  is  as  follows:  Extend  the  tube  to  practically 
its  full  length,  insert  funnel  plug  (not  shown  in  cut),  and 
fill  with  the  sugar  solution  through  one  end  in  the  same 
way  as  a  tube  of  the  ordinary  type.1  Remove  plug,  and 
shorten  the  tube  a  little  by  moving  the  pinion  (N)  slightly. 

1  The  tube  at  the  funnel  end  requires  a  cover  glass  larger  than  the  ordinary 
size. 


POLARIZATION  OF  CANE  SUGAR  95 

This  will  make  the  solution  fill  up  the  plug  hole.  Put  the 
funnel  (7")  in  place  and  fill  about  a  quarter  full  with  the 
solution,  taking  care  not  to  let  air  into  the  main  tube  when 
inserting  the  funnel.  It  is  advisable  to  pour  a  few  drops 
of  the  solution  through  the  funnel  before  placing  the  latter 
in  the  tube,  as  this  insures  displacement  of  the  air  in  the 
neck,  which  might  otherwise  be  forced  into  the  tube.  The 
pinion  should  work  stiffly  enough  to  avoid  changing  the 
length  of  the  control  tube  in  handling.  Owing  to  the  ab- 
sorption of  the  packing  of  the  telescoping  joint  at  C,  the 


FIG.  24.  —  CONTROL  TUBE. 

control  tube  must  be  much  more  thoroughly  rinsed  with 
the  solution  than  an  ordinary  tube,  especially  if  solutions 
are  changed  in  calibrating.  Obviously,  too,  the  tube  must 
be  particularly  carefully  washed  and  dried  after  using.  A 
vented  cap  should  be  used  on  the  funnel  to  avoid  evaporation. 

It  is  vital  for  accurate  work  that  the  temperature  be 
constant  during  the  readings. 

Chemically  Pure  Sucrose  for  Standardizing  Saccharime- 
ters.  —  The  purest  commercial  sugar  (white  granulated  or 
"rock  candy")  is  made  up  to  a  hot  saturated  solution. 
The  sugar  is  precipitated  by  pouring  the  solution  into 
absolute  alcohol,  and  the  crystals  separated  by  a  small 


g6  POLARIZATION   OF  CANE  SUGAR 

centrifugal  and  washed  with  the  same  alcohol.  The  sugar 
is  then  redissolved  and  the  same  procedure  repeated.  The 
crystals  are  then  dried  in  a  vacuum  desiccator  and  kept  in 
a  tightly  closed  glass  vessel. 

Errors  of  Commercial  Polarizations.  —  Besides  the  errors 
of  polariscope  and  saccharimetric  measurements  already 
discussed,  there  are  others  peculiar  to  the  standard  com- 
mercial method,  and  dependent  on  the  nature  of  the 
impurities  present  in  the  sugars  themselves.  Although 
an  immense  amount  of  work  has  been  done  in  the  investi- 
gation of  these  errors,  yet  they  are  little  understood,  and 
practically  are  ignored  in  commercial  analysis  for  the  chief 
reason,  perhaps,  that  experience  has  shown,  in  the  case  of 
the  ordinary  class  of  commercial  sugars,  that  the  total 
errors  apparently  balance  each  other  very  closely,  with 
the  result  that  polarizations  made  at  average  room  tem- 
perature by  the  standard  commercial  methods  give  with 
requisite  accuracy  the  per  cent  of  sucrose  in  the  sample. 
The  effect  of  temperature  variation  -has  already  been  noted. 

The  bulk  of  the  precipitate  from  the  lead  clarification 
has  always  been  neglected  in  commercial  polarizations, 
being  reckoned  as  part  of  the  solution  in  making  up  to 
volume,  partially  on  the  ground  that  its  volume  largely 
results  from  water  of  hydration  abstracted  from  the  solu- 
tion. Many  investigations  have  been  made  to  determine 
the  volume  of  this  dried  precipitate,  as  well  as  in  study  of 
the  effects  of  adding  to  sugar  solutions  known  volumes  of 
material  of  a  nature  supposed  to  be  similar  to  the  impuri- 
ties present  in  the  natural  products.  None  of  this  work 
has  thrown  much  light  on  the  question,  partially  from  the 
difficulty  in  getting  at  the  exact  conditions  of  the  forma- 


POLARIZATION  OF  CANE   SUGAR  97 

tion  of  the  precipitate,  and  also  because,  in  the  case  of  low- 
grade  sugars,  where  this  effect  of  the  precipitate  volume 
is  greatest,  the  lead  solution  exerts  other  little-understood 
influences  on  the  rotation  of  other  impurities  present. 
Therefore,  the  disturbing  effect  is  the  resulta'nt  of  several 
influences,  varying  with  the  nature  of  the  impurities  and  the 
conditions  of  clarifying.  These  errors  in  general  seem  to 
increase  the  polarization,  while  temperature  errors  as  a  rule 
decrease  the  readings.  Consequently,  it  is  questionable,  in 
the  interests  of  scientific  accuracy,  whether  any  correction 
should  be  made,  in  raw  sugar  polarizations  at  least,  till  all 
the  disturbing  influences  can  be  accurately  controlled. 
Otherwise  nothing  is  gained  in  the  approach  to  the  true 
saccharimetric  value.  As  already  stated,  there  has  been 
a  general  agreement  among  sugar  chemists  to  make  polari- 
zations at  20°.  Scheibler  first  devised  a  method  of  "  double 
dilution  "  to  eliminate  the  effect  of  the  bulk  of  the  precipi- 
tate. His  method,  as  modified  by  Wiley,  requires  two  polar- 
izations to  be  made,  one  of  a  solution  made  up  at  the 
normal  concentration,  the  other  at  a  concentration  of  twice 
the  dilution,  that  is,  the  normal  weight  of  sample  dissolved 
in  200  cubic  centimeters  of  solution,  the  amount  of  lead 
acetate  solution  added  before  making  up  to  volume  being 
exactly  the  same  in  both  cases.  It  can  be  shown  mathe- 
matically,1 that  if  a  represents  the  reading  of  the  normal 
solution,  and  b  that  of  the  diluted  solution,  then  the  true 
reading  of  the  solution  at  an  actual  concentration  of  the 
normal  weight  in  100  cubic  centimeters  will  be  given  by 

the  formula,  R  — -.  - 

a  —  b 

1  Wiley,/.  Am.  Chem.  Soc.  18,  430. 


98  POLARIZATION  OF  CANE  SUGAR 

The  lower  grade  raw  cane  sugars,  as  also  cane  juices 
and  sirups,  always  contain  an  appreciable  amount  of  the 
glucose  type  of  sugars.  These  are  to  some  extent  present 
in  the  original  cane  juice,  and  in  part  are  formed  from  the 
decomposition  of  the  cane  sugar  in  manufacture.  Whether 
the  glucose  sugars  from  these  different  origins  are  identi- 
cal or  not  has  not  been  settled  by  sugar  chemists.  It  is 
known  that  the  mixture  of  glucoses  from  the  decomposi- 
tion of  cane  sugar  have  a  left-rotatory  effect,  while  there 
is  much  evidence  that  the  glucose  sugars  in  commercial 
cane  products  are  optically  inactive.  Moreover,  it  is  known 
that  basic  lead  acetate  changes  the  rotations  of  these  glu- 
coses, certainly  in  the  case  of  those  which  are  derived  from 
the  decomposition  of  the  cane  sugar  during  manufacture. 
Although  these  facts  are  most  suggestive,  they  have  not 
yet  led  to  any  accurate  methods  of  estimation  of  the  errors 
of  polarizations  introduced  by  the  action  of  lead  acetate, 
or  their  prevention.  The  addition  of  acetic  acid  to  break 
up  these  levulose  compounds  is  a  questionable  expedient. 

Beet  sugar  products,  even  of  low  grade,  are  practically 
free  from  reducing  sugars,  but  contain  small  quantities  of 
a  polysaccharide  substance  known  as  raffinose.  This  has 
a  strong  specific  rotatory  power  (about  105°)  and  in  some 
cases  makes  an  appreciable  error  in  polarization. 

Errors  due  to  Change  in  Specific  Rotation  of  Sucrose  at 
Low  Concentrations.  —  The  specific  rotation  of  cane  sugar 
is  not  exactly  a  constant  at  all  concentrations  of  its  aqueous 
solution,  as  has  already  been  stated.  Hence,  the  readings 
of  sugar  solutions  of  different  concentrations  on  the  sac- 
charimeter  are  not  strictly  proportional  to  the  thickness 
of  the  compensating  quartz  section,  if  the  saccharimeter 


POLARIZATION  OF  CANE  SUGAR 


99 


is  graduated  so  that  any  reading  n  represents  a  position 
of  the  wedge  corresponding  to  a  section  of  compensating 

quartz  —  of  the  thickness  of  quartz  compensating  at 
the  100  point.  In  other  words,  a  quartz-wedge  saccha- 
rimeter  whose  wedge  surfaces  are  perfect  planes  and 
whose  scale  divisions  are  equal  does  not  give  a  perfectly 
exact  reading  of  the  sugar  per  cent  at  all  parts  of  the  scale. 
Schmitz  has  calculated  the  following  table  giving  the  exact 
saccharimetric  value  for  each  division  of  the  saccharimeter : 


READING 

PER  CENT 

OF  SUGAR 

READING 

PER  CENT 
OF  SUGAR 

READING 

PER  CENT 
OF  SUGAR 

READING 

PER  CENT 
OF  SUGAR 

I 

1.  00 

26 

25.94 

51 

50.92 

76 

75-94 

2 

1.99 

27 

26.94 

52 

5^92 

77 

76.94 

3 

2.99 

28 

27-93 

53 

52.92 

78 

77-94 

4 

3.99 

29 

28.93 

54 

53.92 

79 

78.94 

5 

4.98 

30 

29.93 

55 

54.92 

80 

79-95 

6 

5.98 

31 

3°-93 

56 

55-92 

81 

80.95 

7 

6.98 

32 

3L93 

57 

56.92 

82 

8i.95 

8 

7.98 

33 

32.93 

58 

57.92 

83 

82.95 

9 

8.97 

34 

33-93 

59 

58.92 

84 

83.95 

10 

9.97 

35 

34.92 

60 

59.92 

85 

84.96 

ii 

10.97 

36 

35.92 

61 

60.92 

86 

85.96 

12 

11.97 

37 

36.92 

62 

61.92 

87 

86.96 

13 

12.96 

38 

37.92 

63 

62.92 

88 

87.96 

H 

13.96 

39 

38.92 

64 

63.92 

89 

88.97 

15 

14.96 

40 

39-92 

65 

64.92 

90 

89.97 

16 

15.96 

4i 

40.92 

66 

65.93 

9i 

90.97 

17 

16.95 

42 

41.92 

67 

66.93 

92 

91.98 

18 

17-95 

43 

42.92 

68 

67.93 

93 

92.98 

19 

18.95 

44 

43.92 

69 

68.93 

94 

93.98 

20 

19.95 

45 

44.92 

70 

69.93 

95 

94.98 

21 

20.95 

46 

45-92 

7i 

70-93 

96 

95.98 

22 

21.94 

47 

46.92 

72 

71.93 

97 

96.99 

23 

22.94 

48 

47.92 

73 

72-93 

98 

97-99 

24 

23-94 

49 

48.92 

74 

73-94 

99 

98.99 

25 

24.94 

50 

49-92 

75 

74-94 

100 

IOO.OO 

100          POLARIZATION  OF  CANE  SUGAR 

Some  of  the  modern  saccharimeters  are  graduated  to 
give  strictly  correct  readings  of  sugar  per  cents  at  all 
parts  of  the  scale.  Apparently  this  is  done  by  giving  a 
slightly  curved  surface  to  the  wedge.1 

SOME  IMPORTANT  PAPERS  ON  ERRORS  IN  SUGAR  POLARIZATIONS 

Welz— 1867.     Zeit.  Ver.  deut.  rub.  zuck.  Ind.,  17,  489. 

Maumene — 1870.     Comptes  rendus,  69,  1306. 

Scheibler —  1870.     Zeit.  Ver.  rlib.  zuck.  Ind.,  20,  218. 

Gill,  C.  H.—  1871.     J.  Am.  Chem.  Soc. 

Scheibler —  1875.     Zeit.  Ver.  deut.  rlib.  zuck.  Ind.,  25,  1054. 

Scheibler —  1876.     Ibid.,  26,  724. 

Schmitz  —  1878.     Ibid.,  28,  65. 

Meissl — 1879.     Ibid.,  29,  1034. 

Raffy —  1880.     Neue  Zeit.  Ver.  nib.  zuck.  Ind.,  4,  241. 

Reichardt  and  Bittman—  1882.     Zeit.  Ver.  deut.  rub.  zuck.  Ind.,  32, 

764. 

Sachs —  1884.     Neue  Zeit.,  13,  136. 
Andrews  —  1889.     Tech.  Quart.,  4,  367. 
Andrews  —  1 889.     Ibid.,  4,  371. 

Weisberg —  1891.     Bull.  Assoc.  Chim.  Sue.  et  Dist.,  9,  497. 
Moor — 1894.     La.  Planter,  20,  409. 

Svoboda —  1896.     Zeit.  Ver.  deut.  rlib.  zuck.  Ind.,  46,  107. 
Wiley — 1896.     J.  Am.  Chem.  Soc.,  18,430. 
Pellet—  1896.     Bull.  Assoc.  Chim.  Sue.  et  Dist.,  14,  131. 
L.  de  Bruyn  and  van  Ekenstein  —  1896.     Zeit.  riib.  zuck.,  46,  672. 
Wiley  — 1899.     J.  Am.  Chem.  Soc.,  21,  568. 
Wiechmann —  1903.     Columbia  Sch.  of  Mines  Quart.,  25. 
Horn —  1904.     J.  Am.  Chem.  Soc.,  26,  186. 
Sawyer — 1905.     J.  Am.  Chem.  Soc.,  26,  1631. 

1  The  readings  of  a  quartz  plate  on  an  instrument  graduated  in  the  standard 
Ventzke  scale  averaged  96.02.  The  same  plate  read  95.77  on  a  saccharimeter 
graduated  for  true  cubic-centimeter  flasks.  This  gives  the  ratio,  1.0026:  !<. 
which  approximates  to  the  theoretical  1.00234  :  I. 

A  plate  reading,  62.66  on  the  Ventzke-scale  saccharimeter,  read  62.45  on 
the  new  scale  instrument,  making  the  ratio  1.0033  :  *•  This  is  practically  the 
reading  corrected  for  its  true  sugar  value  by  Schmitz's  table,  which  is  62.43. 

The  readings  of  the  Ventzke  scale  instrument  were  proportional  to  the 
quartz  rotation. 


DETERMINATION  OF  SUCROSE  IN  PRESENCE 
OF  OTHER  OPTICALLY  ACTIVE  SUB- 
STANCES (DOUBLE  POLARIZATION) 

Fundamental  Principles.  —  In  the  methods  of  saccha- 
rimetry,  previously  described,  it  has  been  assumed  that 
sucrose  is  the  only  optically  active  substance  in  the  solu- 
tions polarized.  This  is  practically  true  in  most  commer- 
cial polarizations,  the  error  rarely  exceeding  .2  per  cent 
except  in  low-grade  products,  where  great  accuracy  in  the 
determination  is  not  so  essential.  In  molasses  and  sirups, 
however,  the  presence  of  optically  active  substances  other 
than  sucrose  may  make  errors  of  several  per  cent  in  the 
polarization. 

In  most  molasses  and  natural  cane  sirups  the  principal 
disturbing  optically  active  substance  present  is  known  as 
"invert  sugar."  A  brief  review  of  the  simpler  principles 
of  sugar  chemistry  may  be  of  aid  in  understanding  the 
nature  of  invert  sugar  and  the  methods  of  polarization 
necessary  when  it  is  present. 

Cane  sugar,  or  sucrose,  is  one  of  a  class  of  isomeric 
sugars  known  as  "  saccharoses  "  or  "hexose  bioses,"  from 
the  fact  that  in  chemical  classification  saccharoses  may  be 
considered  as  anhydride  combinations  of  two  molecules  of 
glucose  sugar.  There  are  but  two  other  biose  sugars  of 
present  commercial  consequence,  lactose,  or  milk  sugar, 


IO2  DOUBLE  POLARIZATION 

and  maltose,  or  malt  sugar,  the  latter  being  only  known 
in  commerce  as  a  constituent  of  many  food  products.  The 
formula  expressing  the  percentage  composition  of  these 
saccharoses  is  C12H22On,  or,  better  expressed  from  its 
relation  to  the  glucoses,  (C6HnO5)2O.  Aqueous  solutions 
of  bioses  in  the  presence  of  acids  or  unorganized  ferments, 
which  latter  are  products  of  animal  and  vegetable  life  and 
known  as  "enzyms,"  absorb  an  equivalent  of  water,  and 
are  converted  into  two  glucose  sugars,  cane  sugar  into 
dextrose  and  levulose,  lactose  into  galactose  and  dextrose, 
maltose  into  two  molecules  of  dextrose.  All  of  these 
glucoses  are  isomeric,  having  the  common  proportional 
formula,  C6H12O6,  although  differing  in  molecular  struc- 
ture and  in  many  chemical  characteristics.  This  hydra- 
tion  of  a  saccharose  to  a  glucose  sugar,  which  is  known 
as  "hydrolysis,"  can,  therefore,  be  expressed  by  the  fol- 
lowing simple  equation : 

(C6Hn06)20  +  H20  =  2  C6H1206. 

The  rapidity  of  hydrolytic  action  depends  on  the  chemi- 
cal energy  of  the  acid  or  enzym,  known  as  the  "  hydrolyte," 
and  in  the  case  of  acids  is  greatly  augmented  by  increase 
of  temperature.  Many  salts  and  metals  also  have  pro- 
nounced hydrolytic  action.  This  action  is  always  "  cata- 
lytic," as  the  hydrolyte  does  not  enter  into  chemical  com- 
bination with  the  products  formed,  as  far  as  is  known,  but 
remains  unchanged. 

Concentrated  aqueous  sugar  solutions,  even  when  shown 
to  be  free  from  acid  by  ordinary  chemical  tests,  are 
inverted. appreciably  at  boiling  temperature.  On  this  ac- 
count, in  modern  sugar  manufacture,  all  concentration  is 


DOUBLE  POLARIZATION  1 03 

done  in  vacuum  apparatus,  so  that  boiling  takes  place  at 
a  comparatively  low  temperature  (about  50°  C.). 

In  the  case  of  cane  sugar  hydrolysis,  the  following 
structural  formulae  express  the  reaction : 

CH-^O     CH2OH                   HCO  CH2OH 

/CHOH     ^C                           CHOH  CO 

\  CHOH    /CHOH                    CHOH  CHOH 

VCH       \CHOH"  "HOCH  CHOH 

CHOH     \H                        CHOH  HOCH 

C2HOH      CH2OH                    CH2OH  CH2OH 

(sucrose)  (water)        (dextrose)          (levulose) 

[0^=66.5°  !>]/>=  52.7°        [a]z>=-93° 

The  resulting  mixture  of  the  two  sugars,  dextrose  and 
levulose,  is  known  as  "invert  sugar,"  and  the  hydrolysis 
is  called  "inversion,"  because  of  the  change  in  specific 
rotatory  power  of  the  mixture  from  a  dextrorotatory  value 
(-f )  to  a  levorotatory  (  — ).  The  specific  rotatory  power 
of  sucrose  is  66.5°  at  20°  C.,  that  of  dextrose  52.7°,  and  of 
levulose  —93°.  The  specific  rotatory  power  of  the  result- 
ant mixture  of  equal  equivalents  of  these  two  sugars  has 
become,  therefore,  about  —  20°.  It  will  also  be  evident  why 
these  glucose  sugars  have  received  the  names  they  bear. 

All  cane  molasses  and  sirups  contain  invert  sugar, 
varying  from  a  fraction  of  a  per  cent  up  to  25  per  cent 
or  more.  This  fact  may  be  due  in  part  to  the  presence  of 
the  glucoses  in  the  natural  juice,1  or  to  inversion  of  some 

1  Many  authorities  hold  that  the  glucoses  of  the  cane  plant  are  not  present 
as  constituents  of  invert  sugar,  as  apparently  they  are  optically  inactive.  This 
point  has  been  touched  upon  in  the  previous  chapter,  as  well  as  the  possible 
bearing  of  the  action  of  basic  lead  acetate  on  the  rotation  of  invert  sugar. 


104  DOUBLE   POLARIZATION 

sucrose  during  the  handling  of  the  cane  or  the  manufactur- 
ing of  the  sugar. 

Evidently,  every  equivalent  of  invert  sugar  by  its  left- 
rotatory  effect  neutralizes  the  right-rotatory  effect  of  about 
one  third  of  the  same  equivalent  of  sucrose,  and  the  sac- 
charimeter  underreads  the  true  sugar  per  cent  by  that 
amount. 

Often  in  commercial  table  sirups  r^/-rotating  sub- 
stances are  present,  as  in  mixtures  of  "commercial  glu- 
cose," which  has  a  specific  rotation  of  130°  or  more. 

Clerget  Method  of  Double  Polarization.  —  Clerget,  in  1849, 
first  devised  a  practical  working  method l  for  the  estimation 
of  cane  sugar  in  the  presence  of  other  optically  active 
substances.  The  method  depends  on  the  following  prin- 
ciples:  (i)  Cane  sugar,  alone  of  the  optically  active  sub- 
stances with  which  it  is  ordinarily  associated  in  commercial 
products,  undergoes  a  change  affecting  its  rotatory  power 
when  hydrolized  with  hydrochloric  acid,  provided  that 
this  treatment  is  carried  out  under  the  strictly  limiting 
conditions  defined  by  the  process.  This  change  is  due 
to  a  complete  inversion  of  the  cane  sugar.  (2)  A  definite 
weight  of  cane  sugar  has  its  rotation  changed  by  inversion 
by  a  constant  number  of  divisions  of  the  saccharimeter  at 
any  definite  temperature.  (3)  Hence  the  amount  of  change 
in  rotation  by  inversion  of  a  definite  weight  of  any  sample 
is  proportional  to  the  cane  sugar  it  contains,  and  bears  a 
constant  ratio  to  the  amount  of  change  in  rotation  occur- 
ring under  similar  conditions  in  the  same  weight  of  pure 
sugar.  This  ratio,  therefore,  expresses  the  percentage  of 
sugar  in  the  sample.  (4)  As  the  specific  rotation  of  the 

1  Ann.  Ckim.  Pkys.  26  (3),  185. 


DOUBLE   POLARIZATION  1 05 

levulose  formed  by  the  inversion  decreases  by  increase  of 
temperature,  the  temperature  influence  must  be  considered 

(in  the  calculation.     (5)  As  the  amount  of  change  in  rota- 
"*tion.  (the   algebraic   difference    between    the   polariscope 
readings  before  and  after  inversion)  alone  is  the  measure 
'    of  the  cane  sugar  present,  and  since  cane  sugar  alone  is 
•   changed  by  the  process,  the  rotatory  effects  of  the  other 
optically  active  substances  have  no  influence  on  the  results. 
The  difference  between  the  two  readings  and  not  their 
magnitudes  is  the  measure. 

The  normal  weight  of  pure  cane  sugar  reading  100  on 
the  saccharimeter,  when  inverted  by  hydrochloric  acid 
under  the  conditions  denned  by  Clerget,  reads  —  34  at 
20°.  The  total  change  in  the  reading  is,  therefore,  134 
divisions.  At  o°  the  difference  is  144,  and  at  any  temper- 
ature t  can  be  expressed  as  144 If  then  the  normal 

2 

weight  of  sample,  polarized  under  standard  commercial 
conditions,  gives  a  reading  of  a  on  the  saccharimeter,  and 
a  reading  b,  when  inverted  and  polarized  by  Clerget's 
method,  the  per  cent  of  sugar  in  the  sample  will  be 


i44-^ 

( If  any  weight  of  sample  other  than  the  normal  is  used, 

N 
multiply  by  — 

What  is  practically  the  original  method  is  as  follows : 
Prepare  and  polarize  the  sample  by  the  standard  com- 
mercial method,  but  using  the  half-normal  weight  if  the 
sample  is  highly  colored.  Save  the  filtrate,  prepared  for 


IO6  DOUBLE  POLARIZATION 

the  direct  polarization,  for  inversion.  Take  50  cubic 
centimeters  of  this  nitrate  in  a  50-5  5 -cubic-centimeter 
double  marked  flask,  and  add  hydrochloric  acid  of  a 
density  of  1.20  to  the  55  mark.  Mix,  and  heat  gradually 
to  68°,  taking  fifteen  minutes  to  reach  this  temperature. 
Then  cool  at  once  under  running  water  to  room  tempera- 
ture. Allow  any  precipitate  of  lead  chloride  to  settle  out, 
and  polarize  in  a  2.2-decimeter  tube  provided  with  a  ther- 
mometer,1 which  is  read  to  0.1°  when  the  solution  is 
polarized.  If  the  ordinary  2-decimeter  tube  is  used,  the 
saccharimeter  reading  must  be  increased  by  10  per  cent, 
since  it  has  been  necessary  to  increase  the  volume  by  that 
amount,  in  order  to  add  the  necessary  amount  of  acid. 
A  water  bath  is  the  usual  method  of  heating  the  flask,  but 
a  double-walled  oven  heated  by  boiling  xylol,  which  gives 
an  interior  temperature  of  about  120°,  will  heat  the  solution 
to  68°  in,  very  closely,  the  right  time  interval.  A  water- 
jacketed  oven  is  too  slow,  requiring  a  preliminary  heating 
of  the  flask  to  about  45°  in  a  flame. 

If  the  time  interval  is  too  short,  inversion  is  not  com- 
plete, and  if  the  heating  is  prolonged,  or  the  temperature 
of  68°  exceeded,  some  levulose  is  decomposed.  The 
conditions  of  the  inversion  must  be  strictly  adhered  to. 
(Note  that  zero  errors  of  minus  readings  have  corrections 
in  the  opposite  sign  to  those  of  plus  readings.) 

The  Clerget  method  is  valuable  in  many  investigations, 
but,  obviously,  judgment  must  be  used  in  its  application, 
for  it  is  clear  that  such  a  strong  hydrolytic  agent  as 
hydrochloric  acid  will  in  many  cases  act  upon  the  rotatory 
substances  present.  When  "  commercial  glucose "  is 

1  See  Fig.  23,  p.  93 ;   also  footnote,  p.  90. 


DOUBLE  POLARIZATION 


107 


present  in  large  amount,  an  error  amounting  to  some 
tenths  of  a  per  cent  is  introduced,  owing  to  the  slight 
hydrolysis  of  this  substance  during  inversion  of  the  cane 
sugar.1  Many  prefer  the  modified  German  method  of 
Herzfeld,2  which  is  somewhat  more  complicated,  but  uses  a 
more  dilute  acid  solution,  and  is  more  accurate  in  samples 
of  low  sugar  content,  as  it  takes  into  consideration  the 
change  in  factor  caused  by  the  change  in  the  specific 
rotation  of  levulose  due  to  dilution.  The  German  method 
takes  the  half-normal  weight  of  sample,  which  is  dissolved 
in  75  cubic  centimeters  of  water  in  a  loo-cubic-centimeter 
flask,  $  cubic  centimeters  of  hydrochloric  acid  of  a  density 
of  1. 1 9.  added,  and  the  volume  made  up  to  the  mark,  and 
heated  on  a  water  bath  to  67-70°,  and  then  kept  at  that 
temperature  for  5  minutes,  the  whole  heating  taking  from 
7^  to  10  minutes.  The  factor  of  change  in  rotation  varies 
with  the  concentration,  being  given  in  the  following  table : 


GRAMS 

GRAMS 

GRAMS 

GRAMS 

SUGAR  IN 

SUGAR  IN 

SUGAR  IN 

SUGAR  IN 

100  CUBIC 

FACTOR 

TOO  CUBIC 

FACTOR 

100  CUBIC 

FACTOR 

loo  CUBIC 

FACTOR 

CENTI- 

CENTI- 

CENTI- 

CENTI- 

METERS 

METERS 

METERS 

METERS 

I 

141.85 

6 

142.18 

II 

142.52 

16 

142.86 

2 

141.91 

7 

142.25 

12 

142.59 

17 

142.93 

3 

141.98 

8 

142.32 

13 

142.66 

18 

143.00 

4 

142.05 

9 

142.39 

'4 

H2.73 

19 

143.07 

5 

142.12 

10 

142.46 

15 

142.79 

20 

H3-I3 

As    the    half -normal   weight    is   used,   the   results   are 
multipled  by  2. 

1  Weber  and  McPherson,  /.  Am.  Chem.  Soc.,  17,  319. 

2  Zeit.  Ver.  deut.  nib.  zuck.  Ind.,  38,  699. 


IO8  DOUBLE  POLARIZATION 

Many  modifications  of  the  Clerget  method  have  been 
suggested  with  the  object  of  diminishing  the  possible  de- 
structive influence  of  the  acid  on  the  carbohydrates  other 
than  sugar.  Citric  acid  has  been  used  as  a  hydrolyte,  and 
seems  especially  fitted  for  investigations  of  honeys.  The 
destructive  action  of  the  acid  can  be  greatly  mitigated  by 
carrying  out  the  inversion  at  ordinary  room  temperature. 
The  inversion  is  said  to  be  complete  if  the  Clerget  solution 
is  allowed  to  stand  for  about  eighteen  hours  at  a  tempera- 
ture of  about  20°.  These  modifications,  however,  have  not 
yet  been  developed  into  standard  methods.1 

Determination  of  Sucrose  and  Raffinose.  —  In  beet  molasses 
and  low-grade  beet  sugars,  invert  sugar  is  practically  ab- 
sent, but  an  optically  active  substance  known  as  raffinose, 
of  marked  melassagenic  action,  is  often  present  to  the 
extent  of  several  per  cent.  This  is  a  trios  e  sugar,  being  an 
anhydride  combination  of  three  glucose  sugars,  dextrose, 
galactose,  and  levulose.  Its  specific  rotation  is  104.5°.  By 
hydrolysis  with  acid,  when  the  hydrolytic  action  is  mild, 
raffinose  changes  so  that  its  rotation  becomes  about  half 

1  Tolman  (y.  Am.  Chem.  Soc.,  24,  515)  states  that  hydrochloric  acid  used 
in  inverting  solutions  already  containing  invert  sugar,  as  honeys  and  jams, 
increases  the  levorotation.  Tolman  gives  a  graphical  correction  method  for 
eliminating  this  error,  and  also  states  that  the  variation  in  the  Clerget  factor 
found  by  Herzfeld  is  due  to  this  effect  of  the  acid  on  the  rotation  and  not  to 
differences  in  sugar  concentration.  It  follows  from  this  that,  if  this  influence 
is  done  away  with,  the  Clerget  equation  becomes,  for  all  conditions  of  sugar 
concentration  at  any  given  temperature, 

~  _         a  —  b 

141.85  —  p.5  / 

and  that  the  invert  sugar  per  cent  of  solutions  containing  only  sucrose  and 
invert  sugar  is  given  by  the  equation  : 


-  41.85  +  .  5  / 


DOUBLE   POLARIZATION  IOQ 

as  great.  By  more  energetic  hydrolysis,  the  rotation 
changes  to  one  fifth  the  value.'  The  first  stage  of  the 
inversion  is  the  formation  of  levulose  and  a  biose  sugar 
known  as  melibiose.  By  further  hydrolysis,  the  latter  is 
broken  up  into  galactose  and  dextrose.  Creydt  has  calcu- 
lated formulae  for  adapting  the  Clerget  method  to  the 
estimation  of  sucrose  and  raffinose  in  beet-sugar  products. 
The  readings  are  taken  at  20°,  the  inversion  being  carried 
out  according  to  the  German  modification  of  Clerget's  pro- 
cess. The  formulae  are  based  on  the  fact  that  the  change 
in  rotation  of  a  sucrose  solution  of  normal  concentration, 
by  inversion,  is  from  100  to  —32.66  at  20°  C.,  while  the 
normal  solution  of  raffinose  changes  from  185.2  to  94.9 
saccharimetric  divisions  under  the  same  conditions. 
The  equations  are  as  follows  : 

for  sucrose,  s  = 

for  raffinose.  R  = 


.8390 

£> 


1.852 

a  being  the  direct  reading;   b  being  the  reading  after  in- 
version, of  the  normal  weight  of  sample.     5  and  R  are  the 
per  cents  of  sucrose  and  raffinose  respectively. 
The  equations  are  derived  as  follows  : 

tf=S+  1.852^;  (i) 

b  =  —  .3266  5  +  .949  R.  (2) 

Multiplying  (i)  by    -949  (=  .5124),  and  subtracting  (2) 
1.852 

from  it  gives  .5124*2—  b  =  .8390  5. 

The  method  of  Creydt  has  been  modified  in  a  number  of 
ways,  more  particularly  with  the  object  of  obtaining  better 


HO  DOUBLE   POLARIZATION 

clarification,  as  the  principal  difficulty  is  with  the  darken- 
ing of  the  inverted  solutions.  The  use  of  zinc  dust  in  the 
inverted  solution  as  a  bleaching  agent  has  proved  advan- 
tageous, and  is  the  feature  of  several  of  these  modified 
processes.1 

Speaking  in  general  of  double  polarization  methods, 
none  of  them  are  of  universal  application ;  but,  if  the  prin- 
ciples involved  are  thoroughly  understood,  they  can  be 
applied  to  great  advantage  when  modified  by  the  intelligent 
chemist  to  suit  the  requirements  of  the  analysis. 

1  See:  Lindet,  Sug.  Cane,  1889,  542;  Courtonne,/.  des fab.  de  Sue.,  1890; 
Herzfeld,  Zeit.  d.  V.  f.  Riibenzucker-Ind.,  1890,  165;  Davoll,  /.  Am.  Chem. 
Soc.,  1903,  1019;  Fruhling,  Anleit.  z.  Untersuchung  der  Rohmaterialen  (etc.) 
fur  die  Zucker Industrie,  6th  ed.,  p.  92. 


SUGARHOUSE   AND   REFINERY   METHODS 

IT  is  not  intended  to  discuss  in  detail  either  laboratory 
methods  or  processes  of  sugar  manufacture,  as  there 
are  many  excellent  treatises  exclusively  devoted  to  these 
matters.  The  subject  will  be  dealt  with  very  generally, 
to  illustrate  the  nature  of  the  work  required  of  the  sugar 
chemist,  who  often  is  made  responsible  for  the  manage- 
ment of  the  factory  work  itself.  He  should  seek  to  master 
thoroughly  the  chemical  and  engineering  principles  on 
which  the  work  is  based,  rather  than  simply  learn  details 
of  special  methods  and  processes.  Local  conditions  of 
one  sugarhouse  often  require  radical  changes,  and  the 
development  of  a  scheme  of  work  differing  materially 
from  that  in  practice  elsewhere.  In  this  chapter,  certain 
basic  methods  only  will  be  enlarged  upon,  and  a  scheme  of 
chemical  control  of  a  cane-sugar  house  given  as  merely 
suggestive  of  how  such  work  is  done. 

In  the  manufacture  of  sugar  from  the  cane,  as  a  finished 
product  for  the  consumer,  the  work  is  divided  between 
the  factories  at  the  plantation,  which  make  a  crude  prod- 
uct, and  the  refineries,  that  purify,  decolorize,  and  recrys- 
tallize  this  "raw  sugar."  In  the  United  States,  practically 
all  the  sugar  from  the  cane  reaches  the  consumer  through 
the  refinery.  Beet  sugar,  to  a  large  extent,  is  made  and 
refined  in  the  same  factory,  although  large  quantities  of 
raw  beet  sugars  are  made  in  Europe  specially  for  export. 

in 


112  SUGARHOUSE  AND   REFINERY   METHODS 

Considering  first  the  manufacture  of  sugar  from  cane, 
this  can  be  divided  as  follows  :  (i)  cultivating  and  harvest- 
ing of  the  plant,  and  the  transportation  of  the  canes  to  the 
factory;  (2)  extraction  of  the  juice  in  which  the  sugar  is 
dissolved  from  the  plant  tissues;  (3)  clarification  of  the 
juice  from  colloidal  impurities,  especially  those  which  in- 
terfere with  the  evaporation  of  the  juice  and  consequent 
crystallization  of  the  sugar;  (4)  evaporation  of  the  clari- 
fied juice  to  an  appropriate  density  favorable  for  most 
effective  crystallizing  out  of  the  sugar;  (5)  crystallization 
processes;  (6)  separation  of  the  sugar  crystals  from  the 
mother  liquor,  known  as  "  molasses"  ;  (7)  treatment  of  the 
molasses  by  more  or  less  modified  but  similar  process  for 
the  extraction  of  more  sugar,  but  of  lower  purity,  known  as 
"molasses  sugar." 

(i)  Chemistry  has  only  been  applied  to  a  limited  extent 
in  cane  culture.  Although  there  are  the  beginnings  of 
much  excellent  work  on  fertilizing  and  soil  analysis,  espe- 
cially in  Hawaii  and  Louisiana  (one  very  successful  house 
in  Hawaii  spending  more  than  $100,000  in  scientifically 
prepared  fertilizers),  work  on  this  line  is  not  usually  under- 
taken by  the  factory  chemist,  and  need  not  be  considered 
in  a  treatise  on  sugar  methods.  Agricultural  chemistry 
promises  to  play  an  important  part  in  the  cane-sugar 
_ndustry  of  the  future.1 

1  For  many  centuries  sugar  cane  has  been  cultivated  by  propagation  from 
cuttings,  and  in  consequence  the  plants  are  sterile  as  a  rule.  It  is  only  in 
recent  years,  in  Java,  that  seedlings  have  been  successfully  cultivated.  These 
have  been  obtained  from  plants  which  have  been  induced  to  bear  seed  by 
transplanting  to  the  higher  mountain  levels,  where  conditions  for  growth  were 
unfavorable.  Seedling  farms  have  now  been  established  in  Louisiana,  Barba- 
does,  Cuba,  and  other  cane  countries,  and  are  showing  much  promise  for  the 
economic  improvement  of  the  cane  on  the  lines  so  successful  in  beet  culture. 


SUGARHOUSE  AND    REFINERY   METHODS  113 

Valuation  of  the  Cane.  —  Unlike  the  beet,  sugar  cane 
cannot  properly  be  valued  by  analyses  made  on  laboratory 
samples,  owing  to  the  practically  insuperable  difficulty  of 
obtaining  any  small  lot  of  cane  which  is  representative. 
Different  individual  canes  vary  so  much  that  analyses  of 
one  or  two  are  of  little  value.  The  only  satisfactory  valua- 
tion of  the  cane  is  determined  by  the  quality  of  the  juice 
sampled  from  the  mills  themselves  during  the  grinding  of 
a  lot  of  several  tons.  If,  however,  a  sample  of  at  least  a 
dozen  canes  is  carefully  selected  so  as  to  represent  the 
actual  lot  as  fairly  as  can  be  observed,  and  the  juice  from 
these  canes  is  extracted  by  a  laboratory  three-roller  mill, 
such  as  are  now  specially  made  for  the  purpose,  the  mill 
being  adjusted  and  the  crushing  made  so  as  to  give  an 
extraction  approximating  that  in  actual  practice  in  the  fac- 
tory, the  analyses  will  .agree  very  well  with  those  of  the 
mill  juice  from  the  sugarhouse.  This  will  require  running 
the  sample  canes  three  or  more  times  through  the  experi- 
mental mill.  Such  preliminary  laboratory  tests  are  impor- 
tant in  many  cases,  as  where  it  is  necessary  to  examine  the 
standing  cane  from  the  fields  to  ascertain  its  fitness  for 
grinding,  for  instance ;  but  in  factory  control  the  test  of 
the  juice  actually  obtained  in  the  sugarhouse  is  a  better 
valuation,  and  the  one  usually  relied  on. 

The  cane  coming  to  the  mill  is  weighed  in  the  carts  or 
cars  in  which  it  is  brought.  To  this  weight  all  yields  and 
losses  are  usually  referred  as  percentages,  although  a  better 
basis  of  leference  is  the  weight  of  sugar  in  the  juice  actu- 
ally extracted  or  the  calculated  weight  of  sugar  in  the  cane. 
This  latter  weight,  however,  is  somewhat  approximate,  as 
it  is  practically  impossible  to  obtain  directly  an  accurate 


SUGARHOUSE   AND    REFINERY    METHODS 


determination  of  the  fibre  in  the  cane,  which  is  a  necessary 
datum  for  this  calculation,  owing  to  the  difficulty  already 
alluded  to  of  obtaining  a  representative  laboratory  sample. 
It  should  be  explained  here  that,  for  convenience  in  calcu- 
lation, the  cane  is  arbitrarily  divided  into  two  parts,  juice 
m\&  fibre:  the  juice  being  that  part  which  can  be  extracted 
by  exhaustive  treatment  with  water ;  the  fibre,  the  residue 
after  drying,  —  in  ripe  tropical  canes  about  1 1  per  cent. 
It  consists  of  pentosan  bodies  and  other  insoluble  matter ' 
besides  the  cellulose,  which  is  its  chief  constituent. 

(2)  The  Juice  Extraction.  —  In  the  best  modern  houses, 
the  cane  passes  through  three  mills 1  of  three  rollers  each, 
so  that  it  actually  undergoes  six  crushings.  Sometimes  the 

three  mills  are  com- 
JJ U  ^s~\       ..       ,. 

bined  in  one  machine. 

The  crushed  mass 
coming  from  the  mill 
is  called  "  bagasse," 
and  should  be  a  fri- 
able mass  of  fibre 
barely  moist  to  the 
touch,  although  actu- 
ally containing  about 
50  per  cent  of  mois- 
ture. The  bagasse 
goes  to  the  boiler  furnaces  as  fuel,  and  with  it,  of  course, 
a  certain  amount  of  sugar  in  the  juice  not  completely 
extracted.  This  is  the  first  inevitable  loss  in  manufacture. 

1  Extraction  by  diffusion  is  not  discussed  here,  as  in  most  cane-growing 
countries  this  method  of  juice  extraction  is  impracticable,  owing  to  local  con- 
ditions. Sometimes  the  cane  is  passed  through  a  "  crusher  "  or  "  shredder," 
to  more  thoroughly  disintegrate  it  before  milling. 


FIG.  25. —  SECTION  OF  CANE  MILL. 

(From  Thorp's  "  Outlines  of  Industrial  Chemistry.") 


SUGARHOUSE  AND   REFINERY   METHODS  115 

The  juice  from  the  mills  is  either  weighed  directly  by 
automatic  weighing  machines,  or  its  weight  determined,  as 
is  usual,  by  calculation  from  its  density,  obtained  by  the 
"  Brix  spindle"  (shortly  to  be  described),  and  its  volume, 
measured  in  calibrated  tanks,  usually  the  clarifiers.  The 
weigJit  of  j nice  as  a  percentage  of  tJie  weight  of  cane  ground 
is  known  as  the  "  extraction  "  of  the  mills. 

Ripe  cane  is  treated  with  hot  water,  which  is  commonly 
applied  to  the  bagasse  sheet  passing  between  the  second 
and  third  mills.  This  is  known  as  "  maceration,"  and  con- 
siderably increases  the  extraction.  The  amount  of  water 
added  varies,  according  to  circumstances,  from  5  to  20  per 
cent,  or  more,  of  the  weight  of  the  juice,  and  necessarily  com- 
plicates the  extraction  calculation,  as  will  be  explained  later. 

The  extraction  of  a  modern  sugarhouse  varies  from  72 
to  80  per  cent,  or  more,  according  to  quality  of  the  cane  and 
manner  of  milling.  Often  the  third  mill  juice,  which  only 
amounts  to  a  few  per  cent  of  the  total,  is  treated  separately, 
owing  to  its  greater  impurity ;  and  in  some  factories  lime 
is  added  to  the  bagasse  in  maceration.  These  and  other 
modifications  of  process  require  corresponding  modifica- 
tions in  the  chemical  control,  which  must  be  made  by  the 
chemist  to  suit  the  peculiar  conditions. 

The  juice  coming  from  the  mills  is  a  thin,  opaque  sirup, 
usually  of  a  dark  olive  color,  the  tint  varying  considerably 
according  to  the  condition  of  the  cane  and  the  soil  on 
which  it  is  grown.  Beside  1 5  to  20  per  cent  of  sucrose,  it 
contains  about  .4  per  cent  of  albuminoids,  waxy  matter, 
and  other  plant  extractives.  Small  quantities  of  glucose 
sugars  are  also  present,  in  ripe  cane  less  than  .3  per  cent> 
and  an  insignificant  amount  of  mineral  matter. 


Il6  SUGARHOUSE   AND    REFINERY    METHODS 

The  determinations  on  the  juice  important  for  factory 
control  are  the  sugar  per  cent  and  the  "quotient  of 
purity." 

Quotient  of  Purity.  —  As,  in  the  different  steps  of  sugar 
manufacture,  the  zvater  content  of  the  product  in  process  is 
constantly  changing,  a  simple  polarization  giving  the  per 
cent  of  sugar  on  the  weight  of  sample  is  of  little  value  as 
a  measure  of  the  purity  of  the  product,  unless  made  on  the 
water-free  (anhydrous)  substance.  In  the  necessarily  rapid 
determinations  of  factory  control  it  is  impracticable  to  dry 
each  sample  before  polarizing.  If,  however,  the/^r  cent  of 
total  solids  in  the  sample  can  be  conveniently  obtained,  the 
percentage  ratio  of  the  sugar  per  cent  of  the  sample  to  this 
value  will  be  the  per  cent  of  sugar  in  the  anhydrous  sub- 
stance. As  this  ratio  is  independent  of  the  water  content, 
the  determinations  of  total  solids  and  sugar  percentages 
can  be  made  on  solutions  of  the  sample  at  any  convenient 
concentration,  the  only  condition  being  that  both  tests  are 
referred  to  the  same  concentration. 

This  ratio,  giving  the  per  cent  of  sugar  in  the  anhy- 
drous substance  of  the  sample,  is  known  as  its  "  quotient 
of  purity"  ("  purity  "),  and  can  be  expressed  in  the  equation  : 

T  OO    "P 

Q  =  —     —,  where  P  is  the  polarization  of  the  solution  of 
•^ 

the  product  at  any  convenient  concentration,  and  5  is  the 
per  cent  of  total  solids  at  the  same  concentration. 

Determination  of  Total  Solids.  —  The  density  of  the  solu- 
tion gives  a  rapid  means  of  determining  the  per  cent  of 
total  solids  with  an  approximation  sufficiently  close  for  the 
purpose,  the  assumption  being  made  that  the  impurities 
("  non-sugars  ")  in  the  juice  affect  the  density  in  the  same 


SUGARHOUSE  AND   REFINERY   METHODS  1 1/ 

proportion  as  would  an  equivalent  weight  of  dissolved 
sugar. 

Hydrometers  of  great  precision  are  specially  made  for 
sugar  testing,  which  are  graduated  to  give  at  a  standard 
temperature  (17.5°  C.)  a  direct  reading  of  the  per  cent  of 
:ugar  in  a  pure  solution.  In  solutions  of  the  impure  pred- 
icts of  cane-sugar  manufacture,  such  a  hydrometer  gives 
eadings  expressing  the  per  cent  of  total  solids  very  closely. 

These  hydrometers  are  known  as  "  Brix  spindles  "  or, 
sometimes,  "  Balling  spindles."  Balling  was  the  first  to 
calculate  the  tables  on  which  their  graduation  depends. 
Brix  revised  them  later,  his  values  being  practically  iden- 
tical with  those  of  Balling,  except  at  the  higher  con- 
centrations. The  better  class -of  Brix  spindles  have  a 
thermometer  attached,  and  often  this  thermometer  is 
graduated  to  give  by  direct  reading  the  correction  for 
the  Brix  reading  at  any  temperature  other  than  at  17.5°. 
These  thermometer  graduations  for  the  Brix  temperature 
corrections  are  usually  inexact,  because  the  makers  com- 
monly make  the  assumption  that  the  coefficient  of 
expansion  of  the  solution  is  the  same  as  that  of  pure 
water,  whereas  it  is  perceptibly  greater,  even  at  moderate 
concentrations.  If  such  graduations  are  placed  on  the 
thermometer,  it  should  only  be  done  on  spindles  having  a 
range  of  scale  of  10°  or  less,  and  the  corrections  should 
be  calculated  for  a  concentration  corresponding  to  the 
middle  reading  of  the  scale  of  the  spindle. 

Table  No.  2  (see  Appendix)  should  be  used  for  making 
these  corrections  in  accurate  work. 

Reading  of  Brix  Spindles.  —  Brix  spindles,  like  all  cor- 
rectly made  hydrometers,  should  be  read  along  a  line  lying 


n8 


SUGARHOUSE  AND   REFINERY   METHODS 


in  the  plane  of  the  surface  of  the  liquid  (shown  by  line  a, 
Figure  26),  and  not  at  the  line  of  contact  of  the  liquid  with 
the  stem  (£),  this  line  being  raised  above  the  surface  by  the 
capillary  attraction  of  the  liquid,  to  a  varying  extent  de- 
pending on  the  viscosity  of  the 
liquid.  Some  of  the  Brix  spin- 
dles made  for  commercial  work 
are  graduated  for  15°  C.  or 
60°  F.  Some  sugar  refiners 
use  the  Fahrenheit  scale  on 
their  Brix  spindles,  the  stand- 
ard being  practically  the  same 

asi7.5°C.(63.50)- 

Determination  of  Sugar  in 
Solutions.  —  Owing  to  the  in- 
convenience and  inaccuracy 
of  determining  weights  of 
liquids  by  a  balance,  methods 
have  been  devised  for  polar- 
izing sugar  solutions  without 
the  necessity  of  weighing. 
One  way  is  by  use  of  the 
"sucrose  pipette,"  which  is  a 
FIG.  26.  — ILLUSTRATING  METHOD  pipette  of  the  ordinary  shape 

OF    READING   A    HYDROMETER.          ^      graduated      Qn      the      upper 

stem  with  a  series  of  marks  corresponding  to  degrees  Brix. 
If  the  pipette  is  filled  to  the  mark  corresponding  to  the 
reading  of  the  solution  given  by  a  Brix  spindle  at  the 
temperature  of  observation,  it  will  deliver  the  normal 
weight  of  26.048  grams  of  the  solution.  These  pipettes, 
being  used  for  juice  testing,  are  usually  made  to  deliver 


SUGARHOUSE  AND   REFINERY   METHODS  119 

double  the  normal  weight,  and  so  reduce  the  error  of  the 
small  saccharimetric  readings  correspondingly. 

The  method  of  determining  the  per  cent  of  sugar  in  a 
solution,  generally  used  in  refinery  practice,  depends  on 
the  following  principles : 

As  the  normal  weight  of  pure  sugar,  dissolved  in  100 
cubic  centimeters  of  solution,  when  polarized  in  a  2-deci- 
meter tube,  gives  a  saccharimetric  reading  of  100,  then : 
any  saccharimetric  reading  (R)  of  any  solution  containing 
sugar  (sucrose)  as  the  only  optically  active  substance,  and 

r> 

polarized  in  a  2-decimeter  tube,  shows  that  -  -  of  the  nor- 

i  oo 

mal  weight  of  sugar  must  be  dissolved  in  100  cubic  centi- 
meters of  the  solution.  If  this  value  is  divided  by  the 
density  of  the  solution,1  the  quotient  will  give  the  per  cent 
of  sugar  in  the  solution. 

Hence,  expressing  the  normal  weight  by  N,  and  the 
density  by  d,  the  sugar  per  cent  of  any  solution  (S\  when 
its  saccharimeter  reading  given  by  a  tube  of  standard 
length  (2-decimeter)  is  known,  can  be  found  by  the  follow- 

RN 

ing  equation  :   5  =  —  — . 
100  rf 

In  practical  work,  as  most  solutions  to  which  this  method 
is  applied,  such  as  cane  juices  and  molasses,  have  to  be 
clarified  before  they  can  be  polarized,  it  is  necessary  in 
such  cases  to  allow  for  the  change  in  concentration  of  the 
solution  resulting  from  the  addition  of  the  clarifying  agent. 
This  is  most  conveniently  done  by  the  double-marked  flask, 
such  as  has  been  described  under  the  Clerget  method  of 
double  polarization.  The  flasks  customarily  used  are 
graduated  at  100  and  no  cubic  centimeters,  although  as 

1  See  the  equations  expressing  concentration  of  solutions  on  pp.  12  and  13. 


120  SUGARHOUSE  AND   REFINERY   METHODS 

the  function  of  the  flask  is  to  determine  the  ratio  of  dilu 
tion,  it  is  immaterial  whether  this  size  or  the  50-55  flask  is 
used,  the  errors  of  observation  of  the  reading  of  the 
smaller  volume,  being  well  within  the  other  errors  of 
analysis.  In  such  cases,  obviously,  the  equation  given 
must  be  multiplied  by  j^.  Tables  allowing  for  the 
increase  of  -^  in  the  original  concentration,  and  based 
on  the  equation  given  above,  have  been  designed  by 
Schmitz  for  the  use  of  sugar  chemists.1  These  tables 
give  the  per  cent  of  sugar  directly  when  the  saccharimetric 
and  Brix  readings  are  known,  the  Brix  reading  in  this  case 
being  used  as  an  expression  of  the  density  in  the  calcula- 
tions. The  calculations  of  the  table  are  corrected  for 
slight  changes  in  the  specific  rotation  of  sucrose  at  low 
concentrations  in  very  dilute  solutions.  This  affects  the 
third  significant  figure,  hence  the  table  differs  from  the 
results  obtained  by  the  equation  only  by  that  amount. 

Method  of  Determination  of  Quotient  of  Purity.  —  The 
ordinary  method  of  quotient  of  purity  determination  is  as 
follows :  If  the  sample  is  a  cane  juice,  strain  out  any  par- 
ticles of  bagasse  by  passing  the  juice  through  fine  copper 
gauze,  and  allow  it  to  stand  till  all  the  air  bubbles  have 
escaped.  The  Brix  reading  is  then  taken.  If  the  sample 
is  a  molasses  or  similar  product,  it  is  diluted  to  about  15° 
Brix  before  taking  the  exact  Brix  reading.2  All  Brix  read- 
ings must  be  corrected,  of  course,  to  standard  temperature. 

The  Brix  reading  expresses  the  per  cent  of  total  solids 
in  the  solution,  and  from  the  same  reading  the  density  can 

be  determined  by  a  comparison  table  (see  Table  No.  i  in 

• 

1  See  Table  No.  3  in  Appendix. 

2  See  Hartmann,  Hawaiian  Planter?  Monthly ',  22  (1903),  383. 


SUGARHOUSE  AND    REFINERY   METHODS  121 

Appendix).  A  double-marked  flask  is  now  filled  to  the 
lower  mark  with  the  solution,  the  requisite  amount  of  basic 
lead  acetate  added  to  clarify,  and  the  solution  made  up  to 
the  upper  mark  and  thoroughly  shaken.  The  solution  is 
then  filtered  and  polarized  in  the  ordinary  manner. 

The  refiners  use  their  own  "  exponent  "  books,  which  are 
arranged  in  tables  to  give  the  quotient  ("  exponent")  with- 
out calculation  for  known  Brix  and  saccharimeter  readings, 
the  sugar  per  cents  of  the  liquors  in  process  being  usually 
unnecessary  for  their  records. 

Weisberg's  Method  of  determining  Total  Solids.1 — Another 
ingenious  method  of  determining  the  total  solids  without 
the  use  of  the  Brix  spindle,  only  applicable  to  molasses 
and  other  concentrated  products  denser  than  78°  Brix,  has 
been  devised  by  Weisberg,  and  is  in  practical  use  in  some 
European  houses.  It  is  based  on  the  fact  that,  accord- 
ing to  the  original  Ventzke  standard,  by  which  the  sac- 
charimeter is  graduated,  a  solution  of  the  normal  weight 
(26.048  grams)  of  pure  sugar  dissolved  in  100  Mohr  cubic 
centimeters  has  a  density  of  i.ioco  at  17.5°  C.  referred  to 
water  at  17.5°  as  unity.  As  in  the  Brix  method,  it  also 
makes  the  assumption  that  the  non-sugars  have  the  same 
density  factors  as  the  dissolved  sugar. 

If  26.048  grams  of  the  sample  are  dissolved  in  100  cubic 
centimeters  of  solution,  the  significant  figures  of  the  den- 
sity value,  less  i.oooo,  will  express  the  per  cent  of  total 
solids  in  the  sample.  For  instance,  if  the  density  is  1.0846, 
the  original  sample  contains  84.6  per  cent  solids.  The  sac- 
charimeter reading,  of  course,  gives  the  per  cent  of  sugar 

1  For  other  methods  of  determining  quotient  of  purity,  see  Wiechmann, 
"  Sugar  Analysis." 


122  SUGARHOUSE  AND   REFINERY  METHODS 

in  the  sample,  as  the  solution  is  a  normal  one  for  the 
saccharimeter. 

Quotient  of  purity  determinations  are  of  great  value  to 
the  manufacturer  as  giving  rapid  comparative  figures  for 
determining  the  efficiency  of  the  different  processes.  To 
the  refiner,  particularly,  they  are  indispensable  as  a  basis 
for  planning  the  most  economical  working  of  raw  material, 
often  of  the  most  variable  quality,  into  a  uniform  refined 
product.  Too  much  importance,  however,  should  not  be 
attached  to  exact  numerical  value  expressed  by  the  purity 
figures,  as,  owing  to  the  diverse  nature  of  the  "  non-sugars  " 
under  different  circumstances,  products  of  the  same 
"  purity  "  may  work  up  quite  differently. 

Other  tests  made  on  cane  juice,  of  more  or  less  value 
for  chemical  control  of  the  factory,  are  for  acidity  and 
glucose  sugars.  Acidity  tests  are  usually  expressed  in 
terms  of  decinormal  sodium  hydrate  or  lime  to  neutral- 
ize, using  phenolphthalein  as  an  indicator.  The  glucose 
test  is  not  considered  so  important  as  formerly,  when 
these  sugars  were  supposed  to  have  a  much  greater  effect 
than  they  do  have  upon  the  crystallization  of  the  sucrose. 
As  a  matter  of  fact,  the  glucose  sugars  in  themselves  have 
little  harmful  effect,  but  their  amount  in  juice  from  fresh 
cane  is  to  a  large  extent  indicative  of  its  condition.  Un- 
ripe cane  always  contains  a  larger  proportion  of  glucose, 
which  is  associated  with  albuminoid  (pectenoid?)  sub- 
stances, usually  termed  "  gum."  These  greatly  increase 
the  viscosity  of  the  liquors  in  process,  retarding  evapora- 
tion and  interfering  with  crystallization.  They  are  only 
partially  removed  by  the  ordinary  processes  of  clarifica- 
tion. The  glucoses  are  the  indicator  rather  than  the  dis- 


SUGARHOUSE  AND    REFINERY   METHODS  123 

turbing  cause,  and  as  one  test  for  unripe  cane  this  deter- 
mination has  some  value.1  As  any  destruction  of  sucrose 
by  inversion  due  to  ferments  or  other  cause  produces  glu- 
cose sugars,  any  marked  increase  in  the  "glucose  ratio" 
(the  ratio  of  glucose  to  sucrose)  in  the  products  in  process 
is  evidence  of  inversion;  but  as,  in  the  majority  of  cases, 
these  glucose  sugars  are  destroyed  to  considerable  extent 
during  the  processes  of  clarification  and  in  the  "meladuras" 
(evaporated  sirups),  the  values  of  the  glucose  ratio  must 
be  interpreted  with  considerable  caution.  The  methods 
of  determining  glucose  sugars  will  be  discussed  later. 

Determination  of  Extraction  when  the  Juice  is  diluted 
by  Maceration. — When  the  juice  is  diluted  by  maceration 
water,  the  determination  of  the  amount  extracted  at  its 
original  concentration  is  somewhat  complicated.  In  this 
case  it  is  necessary  to  determine  the  Brix  of  the  juice  from 
the  mill  before  it  is  macerated,  and  also  the  Brix  of  a 
sample  of  the  total  amount  of  completely  mixed  and 
diluted  juice.  The  per  cent  of  maceration  water  will  be 

Z> T) 

given  by  the  following  equation  :   P  =  — ^ — ^   wnere  p 

&\ 
is  the  per  cent  of  maceration  water  in  the  juice,  Bl  is  the 

Brix  of  the  normal  juice,  B%  the  Brix  of  the  diluted  juice. 
From  these  data  the  weight  of  the  normal  juice  can  be 
readily  obtained.2 

1  Ripe  cane,  if  old  and  soured,  of  course,  contains  glucoses  from  the  inver- 
sion.    Such  cane,  if  not  absolutely  rotten,  "works"  easily,  as  the  "gum"  is 
absent,  although  it  gives  a  poor  yield  and  much  molasses. 

2  The  quality  of  the  juice  from  the  different  mills  varies  somewhat,  that 
from  the  later  crushings  having  more  impurities.     Maceration  also  lowers  the 
purity  of  the  juice.     This  small  change  in  quality  of  the  juice  does  not  appre- 
ciably affect  the  calculation  given  here. 


124  SUGARHOUSE  AND   REFINERY   METHODS 

Determinations  on  the  Bagasse.  —  The  per  cent  of  sugar 
in  the  bagasse  is  sometimes  determined  as  a  check  on  the 
extraction  figures,  but  the  most  useful  datum  is  the  fibre 
content,  as  this  can  be  utilized  to  estimate  the  fibre  in  the 
cane  by  calculation  from  the  extraction.  The  extraction 
being  known,  the  per  cent  of  fibre  in  the  bagasse  can  be 
referred  to  the  cane  itself.  The  great  difficulty  in  this 
determination  is  in  the  sampling,  as  not  only  does  the 
bagasse  vary  in  its  nature,  but  it  dries  very  rapidly  in  a 
small  sample.  The  only  proper  sample  is  one  of  at  least 
200  grams.  The  bagasse  should  be  collected  in  a  covered 
box,  in  which  it  should  be  weighed  without  removal  to 
avoid  error  from  evaporation.  The  weighed  sample,  if 
not  well  shredded,  should  be  picked  to  pieces  and  then 
placed  in  a  gauze  basket  and  thoroughly  washed,  prefera- 
bly in  warm  soft  water,  till  the  washings  no  longer  react  for 
sugar.  The  residue,  dried  at  105°  C,  is  taken  as  the  "  fibre." 

Juice.  —  The  juice  should  be  sampled  at  least  once  an 
hour,  the  samples  either  being  tested  at  once  or  measured 
portions  put  in  a  graduated  bottle  in  which  has  been 
placed  a  few  drops  of  mercuric  chloride  solution  to  avoid 
fermentation.  This  general  sample  is  tested  at  regular 
intervals,  three  or  four  times  in  twenty-four  hours.  As 
lots  of  cane  from  different  plantations  are  often  bought  at 
a  price  based  upon  the  quality  of  the  juice  extracted  by  the 
mill,  individual  samples  of  juice  are  also  taken  from  the 
mills  during  the  grinding  of  such  lots  and  tested  separately. 

Conditions,  of  course,  will  considerably  modify  the  chem- 
ical control  methods,  and  many  other  interesting  and  valu- 
able tests  can  be  made  on  the  juice,  such  as  those  which 
throw  light  on  the  nature  of  the  colloidal  non-sugars  and 


SUGARHOUSE   AND    REFINERY   METHODS  125 

their  removal,  the  viscosity  of  the  juices,  etc.  Such  work 
will  depend  on  the  facilities  at  the  disposal  of  the  chemist. 
(3)  The  juice  from  the  mills  next  goes  to  the  clarifiers, 
either  directly  or  after  a  previous  mixture  with  the  precipi- 
tant, and  in  many  cases  a  preliminary  heating  by  the  waste 
heat  from  other  factory  processes,  which  is  thus  econo- 
mized. Clarification  in  raw  cane-sugar  manufacture  is 
a  crude  process  at  best,1  and  is  only  designed  to  remove 
those  impurities  which  have  influence  in  preventing  crys- 
tallization and  evaporation.  These  impurities  are  in  the 
main  of  an  albuminoid  nature,  the  -composition  of  which 
is  little  understood.  They  seem  to  be  of  an  amino  or 
amido  constitution,  related  to  glycocoll  or  asparagine,  and 
xanthin  bases.  They  exist  in  the  juice  in  a  " colloidal" 
or  gelatinous  condition,  and  consequently  have  to  be  pre- 
cipitated before  they  can  be  removed  by  settling  or  filtra- 
tion. There  is  also  a  waxy  substance  from  the  rind  of 
the  cane.  By  bringing  the  juice  to  practically  the  neutral 
point  with  fresh  quicklime  and  heating  to  about  185°  F. 
(85°  C.),  about  50  per  cent  of  the  total  albuminoids  are 
precipitated,  which  is  sufficient  for  raw-sugar  manufac- 
ture. The  special  clarification  or  "  defecation  process," 
as  usually  carried  out,  consists  in  heating  the  limed  juice 
in  shallow  tanks  ("defecators")  provided  with  a  relatively 
large  heating  surface  so  as  to  produce  rapid  enough  con- 
vection to  throw  the  precipitated  albuminoids  and  wax 
to  the  surface,  where  they  remain  as  a  thick  scum  or 

1 A  certain  amount  of  white  sugar  is  made  in  all  sugar  countries  for  local 
consumption.  This  sugar,  as  a  rule,  is  made  from  liquors  which  have  under- 
gone a  second  filtration  and  bleaching  with  sulphur  dioxide,  and  is  carefully 
washed  in  the  centrifugal  machines,  steam  being  used  to  make  dry  crystals. 


126  SUGARHOUSE  AND   REFINERY   METHODS 

"  blanket."  After  the  clarified  juice  is  allowed  to  stand 
till  the  small  amount  of  settlings  deposit,  the  clarified 
juice,  which  in  an  ordinary  test  tube  looked  at  trans- 
versely usually  appears  as  a  clear  yellowish  green  sirup, 
is  decanted  into  tanks  for  further  settling  before  going 
to  the  evaporators.  The  amount  of  lime  required  for 
defecation  varies  considerably  with  its  quality  and  the 
condition  of  the  juice,  for  fresh  ripe  cane  juice,  averaging 
about  6  pounds  per  1000  gallons.  It  may  vary  greatly 
from  this  figure.  The  point  of  proper  defecation  is  prac- 
tically the  neutral  point.  Usually,  but  not  necessarily,  the 
decanted  juice  shows  a  faint  alkalinity  (.002  to  .005  with 
phenolphthalein).  The  exact  point  is  much  better  shown 
by  the  appearance  of  the  precipitated  albuminoids  and  the 
clarified  liquor  than  by  any  of  the  usual  indicators.  Proper 
defecation  is  shown  by  the  appearance  of  a  well-defined 
coagulation,  the  coagulated  matter  being  flocculent  and 
settling  slowly,  leaving  a  practically  clear  sirup.  Over- 
limed  juice  is  dark  colored,  and  the  precipitate  settles 
rapidly.  In  underlimed  juice  the  liquor  is  milky  from 
incomplete  coagulation.  The  odors  also  are  characteristic 
to  an  expert.  Overlimed  juices  make  deposits  on  the  coils 
of  evaporating  apparatus,  and  also  produce  slimy  humus 
products  from  the  decomposition  of  the  glucose  sugars, 
which  interfere  in  the  purging  in  the  centrifugals,  espe- 
cially in  second  sugars.  Overliming  is  a  common  error, 
but  the  consequences  of  underliming  are  more  obvious. 
Often  loam  or  clay  from  canes  which  have  been  beaten 
down  by  winds  or  rains  give  a  turbidity  which  remains  in 
the  decanted  juice  and  is  apt  to  deceive  the  inexperienced. 
This  does  little  harm  if  not  excessive,  and  can  in  the  main 


SUGARHOUSE   AND    REFINERY    METHODS  I2/ 

be  removed  at  the  mills  by  suitable  settling  devices  in  the 
juice  canals. 

In  the  Denting  process  the  continually  passing  juice  is 
heated  in  a  sort  of  digester  under  low  steam  pressure,  the 
heat  of  the  clarified  juice  being  economized  by  being  trans- 
ferred back  to  the  entering  cold  juice,  on  the  principle 
of  the  surface  condenser.  The  coagulated  albuminoids, 
which  are  said  to  be  more  perfectly  separated,  have  a  ten- 
dency to  settle,  and  are,  when  the  process  works  properly, 
removed  from  the  bottoms  of  settling  tanks. 

In  the  older  methods  of  defecation,  the  scums  on  the 
surface  of  the  defecators  were  swept  off  into  draining 
boxes.  In  modern  houses,  they  are  passed  through  filter 
presses.  The  proportion  of  juice  which  passes  through 
the  filter  presses  varies  in  different  sugarhouses,  but  when 
the  defecation  and  decantation  are  properly  carried  out, 
does  not  exceed  15  per  cent,  even  with  poor  juices.  The 
scums  before  passing  through  the  presses  are  cooked  with 
more  lime,  as  this  gives  a  harder  press  cake,  and  the 
slightly  alkaline  juices  neutralize  the  acidity  which  would 
otherwise  result  from  the  enormous  cooling  and  aerating 
surfaces  of  the  presses  with  their  complicated  spaces  in 
which  fermentation  takes  place  at  times  in  spite  of  care. 
The  filter-press  liquors  are  slightly  darker  in  color,  more 
alkaline,  and  of  lower  purity  than  the  decanted  juice. 

Obviously,  the  second  necessary  loss  in  the  house  comes 
from  the  sugar  of  the  juice  left  in  the  press  cake,  and  is 
determined  by  polarizing  a  representative  sample  of  the 
fresh  cake,  allowance  being  made  in  the  weight  of  sample 
taken,  for  the  volume  occupied  in  the  flask  by  the  insoluble 
matter  in  the  cake,  A  few  drops  of  acetic  acid  are  added 


128  SUGARHOUSE   AND    REFINERY   METHODS 

by  some  to  break  up  any  possible  calcium  sucrate  which 
might  be  formed  if  the  liming  is  excessive.  The  normal 
weight  for  filter  cake,  as  usually  taken,  is  25.00  grams, 
which  is  most  conveniently  made  up  to  a  volume  of 
200  cubic  centimeters,  the  saccharimeter  reading,  of 
course,  being  multiplied  by  2. 

The  total  weight  of  cake  is  taken  as  it  is  removed  from 
the  presses,  or  can  be  approximated  with  sufficient  accuracy, 
by  calculation  from  the  number  of  presses  in  use,  by  multi- 
plying by  the  average  weight  of  cake  per  press  determined 
occasionally. 

Other  clarification  and  filtration  processes  are  in  use. 
Often  a  secondary  filtration  is  given  the-  juice  after  clari- 
fication, by  "mechanical,"  or  "sand  filters."  If  the  juice 
is  properly  defecated,  this  secondary  filtration  is  quite 
unnecessary  in  raw  sugar  manufacture. 

The  loss  of  sugar  in  the  filter  cake,  unwashed,  usually 
lies  between  .10  per  cent  and  .15  per  cent  of  the  weight  of 
cane. 

(4)  The  clarified  juice  from  the  settlers  goes  to  the 
multiple-effect  evaporators,  where  it  is  concentrated  to 
about  35  per  cent  of  its  volume,  making  a  sirup  known  as 
"  meladura,"  which  is  ready  for  crystallizing  in  the  vacuum 
pans. 

The  density  at  which  this  sirup  is  concentrated  depends 
on  its  purity,  it  being  difficult  to  crystallize  in  the  vacuum 
pan  from  impure  meladuras  when  very  concentrated.  Very 
pure  meladuras  can  be  worked  up  from  a  density  of  30° 
"  Beaume  "  :  (54-3°  Brix),  but  meladuras  from  unripe  juices 

1  There  are  twenty  or  more  different  Beaume  scales  in  existence.  The 
original  was  made  by  Beaume  by  taking  water  at  12.5°  C.  as  zero,  and  a  10 


SUGARHOUSE   AND   REFINERY   METHODS  1 29 

work  much  better  at  considerably  lower  density.  At  the 
same  time,  it  must  be  understood  that  evaporation  is  done 
far  more  economically  in  the  multiple-effect  apparatus  than 
in  the  vacuum  pan. 

Meladura  is  usually  stored  in  a  series  of  settling  tanks 
of  small  capacity,  so  that  they  can  be  frequently  emptied 
and  cleaned  without  interfering  with  the  work  of  the  house. 
At  least  once  a  week  every  tank  should  be  thoroughly 
cleaned  and  whitewashed,  the  settlings  being  run  off  into 
the  first  molasses  (not  into  the  juice  scums). 

In  the  more  primitive  processes  of  sugar  manufacture, 
which  are  still  extant  in  some  places,  making  what  are 
known  as  "muscovado"  or  "open  kettle"  sugars,  the 
clarification  and  evaporation  to  the  crystallizing  point  are 
carried  on  in  a  series  of  hemispherical  kettles  built  into  a 
brick  furnace.  The  lime  is  added  in  the  first  kettle,  where 
the  main  defecation  occurs,  and  the  juice  as  it  evaporates 
is  ladled  from  one  kettle  to  the  next  till  the  more  concen- 
trated sirup  is  collected  in  the  last.  The  scums  from  the 
defecation  are  swept  in  the  opposite  direction,  and  finally 
from  the  surface  of  the  liquor  in  the  first  kettle  into  a 
draining  box. 

The  tests  of  the  meladura  useful  for  chemical  control 
are,  its  density,  its  purity,  and  its  alkalinity.  The  mela- 
dura should  always  react  faintly  alkaline.  If  it  reacts  acid 
from  any  cause,  milk  of  lime  should  be  stirred  in. 

(5)   The  crystallization  of  the  sugar  from  the  meladura 

per  cent  solution  of  common  salt  as  10.  The  scale  which  is  in  universal  use 
in  the  sugar  industry  is  that  of  Gerlach,  and  is  somewhat  modified  from  the 
original  Beaume.  This  Beaume  spindle  is  exclusively  used  by  workmen  in  the 
sugarhouse. 

K 


130  SUGARHOUSE  AND    REFINERY   METHODS 


FIG.  27.  —  INSTALLATION  OF  VACUUM  PAN  AND  CENTRIFUGALS  IN  A 
SUGARHOUSE. 

V.  Vacuum  pan.  M.   Mixer. 

C.   Centrifugals.  P.  Vacuum  and  condenser  pumps. 

(From  an  old  drawing.) 


SUGARHOUSE   AND   REFINERY   METHODS  131 

by  the  vacuum  pan  can  be  divided  into  three  stages : 
(A)  the  evaporation  of  the  meladura  to  the  point  of  sugar 
saturation;  (£)  the  formation  of  the  crystals,  or  " grain- 
ing " ;  (C)  the  building  up  of  the  crystals  to  the  required  size. 

In  the  first  stage,  the  pan  is  simply  working  as  an  ordi- 
nary evaporator,  the  special  skill  of  the  pan  man  being 
required  in  one  particular,  the  amount  of  "  charge."  This 
must  be  so  regulated  that  the  meladura,  concentrated  to 
the  saturation  point,  will  have  the  requisite  volume  to  allow 
for  the  growth  of  sufficient  crystals  to  just  fill  the  pan  full 
when  the  sugar  is  finished.  This,  obviously,  is  a  matter 
requiring  considerable  experience,  and  is  conditioned  on 
the  quality  of  the  juice,  as  well  as  the  size  of  the  crystals 
required,  and  the  polarization. 

The  starting  of  the  crystallization  is  also  a  matter  re- 
quiring much  skill  and  experience.  As  soon  as  the  first 
"  sparks  "  are  visible  in  the  "  proof,"  taken  out  of  the  pan 
at  frequent  intervals,  the  temperatures  must  be  carefully 
regulated,  usually  by  manipulating  the  condensing  appa- 
ratus. The  "  drinks  "  of  meladura  taken  into  the  pan  must 
be  as  carefully  graduated  so  as  to  regulate  the  amount  of 
the  crystals  which  form,  for  on  this  will  depend  to  a  large 
extent  the  quantity  of  finished  sugar  of  the  required  polari- 
zation, as  well  as  the  size  of  the  crystals  themselves.  If 
the  juice  be  of  poor  quality,  the  meladura  used  to  control 
the  crystallization  at  this  point  must  be  less  dense,  and  the 
temperature  raised,  to  prevent  the  "grain"  forming  too 
rapidly.  After  the  requisite  crystal  foundation  is  estab- 
lished in  the  "  charge,"  subsequent  additions  of  meladura 
must  be  skillfully  made  during  the  rest  of  the  process,  so 
that  the  crystal  growth  will  proceed  regularly  and  con- 


132  SUGARHOUSE  AND    REFINERY   METHODS 

tinuously,  with  the  minimum  production  of  "  false "  or 
"  second  grain."  This  latter  is  caused  by  the  separation 
of  sugar  in  fine  floury  crystals,  independently  of  the  origi- 
nal foundation  grain,  and  cannot  be  avoided  absolutely, 
although  practically  evaded  by  skillful  pan  men.  The 
second  grain,  if  the  crystals  are  too  large  to  pass  the 
screens  of  the  centrifugal  machines,  makes  "purging" 
harder,  and  reduces  the  polarization  of  the  sugar,  owing  to 
the  greater  absorption  (capillarity)  due  to  the  unequally 
sized  grains  packing  more  closely.  If  the  second  grain  is 
fine  enough  to  pass  the  screens,  it  goes  into  the  molasses, 
and  so  reduces  the  yield  of  the  first  sugar. 

Skill  engendered  of  long  experience  and  familiarity  with 
the  working  of  his  pan  are  essential  qualifications  of  a 
first-class  sugar  boiler.  Such  men,  in  raw-sugar  work,  com- 
mand high  pay  and  have  much  responsibility.  An  unskill- 
ful man  may  cause  a  loss  of  hundreds  of  dollars  a  week. 

When  the  sugar  is  finished,  the  pan  is  filled  with  a  stiff 
pasty  mass  of  crystals  and  molasses  in  about  the  proportion 
of  65  per  cent  of  sugar  to  35  per  cent  of  molasses.  This 
is  known  as  "massecuite." 

(6)  The  steam  being  turned  off  and  the  vacuum  broken, 
the  massecuite  is  discharged  into  the  "  mixer,"  where  it  is 
kept  slowly  stirred  till  it  has  all  been  passed  through  the 
"  centrifugal  "  machines,  —  sieves  which  revolve  at  a  speed 
of  a  thousand  revolutions  or  more  per  minute,  by  which  the 
molasses  is  removed,  leaving  a  moist  mass  of  brown  sugar 
crystals.  The  sugar  after  being  cooled  by  fans  is  put  into 
bags  usually  holding  about  300  pounds.1 

In  the  chemical  control,  purity  and  density  tests  of  the 

1  Hawaiian  practice  :   125  pounds. 


SUGARHOUSE  AND   REFINERY   METHODS 


133 


first  massecuite  are  useful,  but  are  not  often  made  part  of 
the  daily  routine. 

The  polarization  of  each  "strike"  of  first  sugar,  as  well 
as  the  weight  obtained,  is  important.  Often  it  is  necessary 
to  follow  the  working  of  [^^ 

the  centrifugal  machines 
during  the  running,  to 
regulate  the  time  neces- 
sary for  purging,  and 
the  amount  of  "  charge  " 
to  turn  out  the  requisite 
quality  of  sugar.  This 
is  done  by  making  polar- 
izations of  samples  at 
once  as  soon  as  the  purg- 
ing begins. 

The  usual  conditions 
require  the  sugar  to 
be  turned  out  as  near 
96  per  cent  as  possible. 
Sometimes  the  sugar  is 
allowed  to  stand  for  some 
hours  in  "coolers,"  or 
wagons,  before  purging. 
This  is  not  commonly 
done. 

/->.  .,  ,  (From  Thorp's  "  Outlines  of  Industrial  Chemistry.") 

One    possible    source 

of  loss  in  vacuum  apparatus  is  from  what  is  known  as 
"entrapment,"  which  is  the  carrying  off  of  sirup  me- 
chanically in  the  current  of  vapors  passing  away  from 
the  apparatus.  The  sirup,  owing  to  its  viscosity, 


FIG.  28.  —  SECTION  OF  WESTON  CENTRIF- 
UGAL MACHINE. 

A.  Sieve  in  side  of  revolving  "basket"  which  re- 

tains the  sugar. 

B.  Shaft  of  basket  on  which  slides  bell  which  closes 

opening  for  discharging  sugar. 

C.  Casing  in  which  collects  the  molasses  discharged 

through  the  sieves. 


134  SUGARHOUSE   AND    REFINERY   METHODS 

escapes,  it  is  said,  in  vesicles  analogous  to  minute  soap 
bubbles. 

Modern  apparatus  is  so  well  designed  that  entrainment 
is  reduced  to  a  minimum  which  is  practically  negligible  in 
good  work.  Occasionally,  steam  coils  in  the  pan  may 
spring  a  leak.  If  the  leak  is  a  small  one,  it  may  not  affect 
£he  working  of  the  pan,  but  when  such  coils  are  shut  off, 
the  vacuum  formed  in  the  coils  causes  sirup  to  enter  them. 
As  the  condensation  water  from  the  coils  is  used  for  boiler 
feed,  the  sugar  may  do  much  damage  by  collecting  in  the 
boilers  and  causing  them  to  foam.  The  "  tailpipes  "  of  all 
vacuum-pan  coils  should  be  provided  with  test  cocks  so 
that  the  "returns"  can  be  frequently  examined  for  sugar. 
The  polariscope  is  hardly  sensitive  enough  to  show  the 
small  quantity  of  sugar  which  it  is  necessary  to  detect  in 
some  cases,  chemical  methods  being  more  applicable. 
Indeed,  the  color  and  odor  of  the  returns  is  sufficiently 
conclusive  of  a  leak.  The  returns  from  the  steam  cham- 
bers of  the  multiple-effect  evaporators  are  also  used  for 
boiler  feed,  so  that  any  entrainment  other  than  from  the 
last  effect  will  also  affect  the  "  sweet  waters  "  (as  they  are 
erroneously  called),  and  do  mischief  to  the  boilers. 

The  Brix,  polarization,  and  quotient  of  purity  are  taken 
of  a  representative  sample  of  first  molasses  from  every 
"  strike  "  of  sugar. 1 

(7)  The  methods  for  further  extraction  of  the  50  per  cent 
or  more  of  sugar  contained  in  the  molasses  vary  much  in 

1  The  most  accurate  way  of  determining  the  total  solids  ("  Brix ")  of  a 
molasses  is  to  dilute  by  weight.  For  instance,  add  to  100  grams  of  the  sample 
sufficient  water  to  make  the  solution  weigh  500  grams.  Five  times  the  Brix 
reading  of  the  solution  will  give  the  total  solids  in  the  molasses  in  this  case. 


SUGARHOUSE  AND   REFINERY   METHODS  135 

different  places.  Usually,  the  molasses  is  diluted  some- 
what, heated  to  dissolve  any  <(  grain"  that  may  be  present, 
and  is  concentrated  in  the  pan  to  the  graining  point,  but 
not  far  enough  to  have  crystallization  actually  take  place. 
It  is  then  run  into  tank  wagons,  or  into  crystallizers,  where 
it  is  allowed  to  remain  till  crystallization  is  complete,  the 
time  being  generally  from  five  days  to  a  week.  This  is 
known  as  "  boiling  blank."  The  massecuite  is  then  purged 
in  centrifugals,  giving  "  second  sugar."  Usually  the  heat 
is  regulated  by  steam  pipes  in  the  "  hot  room  "  where  the 
wagons  are  stored,  so  as  to  retard  the  cooling  and  allow 
a  gradual  growth  of  the  crystals. 

The  "  crystallizer  "  is  a  modern  apparatus  for  controlling 
the  conditions  of  crystallization  more  effectively,  requiring 
less  skill  in  handling  to  obtain  a  uniform  product  than  the 
wagon  methods.  In  its  ordinary  form,  the  crystallizer  is  a 
large  horizontal  cylinder,  holding  twenty-five  tons  or  more, 
provided  with  a  slowly  moving  stirring  apparatus,  and 
arrangements  for  heating  or  cooling  the  contents.  The 
massecuite  is  run  into  the  crystallizer,  where  it  is  allowed 
to  stand  for  a  number  of  hours,  till  the  crystals  have  begun 
to  appear,  and  then  the  mass  is  occasionally  (very  slowly) 
stirred  to  bring  fresh  molasses  in  contact  with  the  crystals. 
The  temperature  is  regulated  accordingly  as  the  crystal- 
lization progresses,  being  also  conditioned  on  local  circum- 
stances. Sometimes,  with  rich  molasses,  the  graining  is 
made  in  the  pan  as  in  the  case  of  first  sugar,  or  the  grain 
is  started  with  meladura,  or  sugar  is  actually  put  in  the 
pan  for  a  grain  foundation. 

Other  methods  are  designed  to  utilize  the  first  molasses 
directly  in  the  formation  of  first  sugar.  In  one,  the  water 


136  SUGARHOUSE  AND   REFINERY   METHODS 

of  the  molasses  of  the  first  massecuite  is  practically  all 
boiled  away,  and  the  hot  molasses  of  the  previous  "  strike  " 
is  injected  at  the  right  moment,  thinning  the  whole  mass 
sufficiently  to  allow  it  to  run  out  of  the  pan.  Sugar  is 
crystallized  out  in  this  way,  and  the  molasses  is  lowered  in 
purity.  In  another  method  the  molasses  is  thinned  to  the 
consistency  of  meladura,  and  an  amount,  dependent  on  its 
purity,  is  used  to  build  up  the  grain  during  the  latter  stages 
of  the  boiling  of  the  first  sugar.  Only  a  part  of  the  total 
first  molasses  can  be  utilized  in  this  way,  the  rest  being 
made  into  "second  sugar.'' 

The  second  sugars  are  polarized,  and  the  tests  for  Brix 
and  purity,  as  well  as  the  polarization,  made  on  the  second 
molasses.  This  latter  is  often  worked  up  for  a  third  sugar, 
but  if  the  processes  of  extraction  of  the  two  sugars  are 
skillfully  carried  out,  most  raw  juices  will  not  pay  for  a 
third  working.  A  good  yield  of  "thirds"  does  not  by  any 
means  always  indicate  good  work.  The  second  sugars  are 
often  remelted  to  a  sirup,  and  worked  up  with  meladura 
into  first  sugars.  In  some  cases  the  sugar  itself  is  put  into 
the  first  massecuite  in  the  mixer. 

The  chemical  control  of  a  raw-sugar  house  carrying  on 
the  process  in  the  general  manner  outlined  is  for  two 
objects:  (i)  the  guidance  of  the  daily  routine  of  the 
house;  (2)  an  accurate  estimation  of  the  total  yields  and 
losses  during  a  definite  period  of  running. 

As  the  sugarhouse  is  running  continuously,  night  and 
day,  most  of  the  material  in  process  is  distributed  through 
the  house,  and  constantly  undergoing  such  change  that 
any  daily  estimate  of  the  yields  and  losses  during  the  actual 
running  is  only  an  approximation  too  rough  to  be  of  value 


SUGARHOUSE  AND   REFINERY   METHODS  137 

in  calculating  the  efficiency  of  the  work.  The  weight  of 
the  cane  and  that  of  the  juice,  giving  the  extraction,  can 
be  estimated  with  reasonable  accuracy,  but,  as  most  houses 
are  arranged,  this  is  the  only  daily  calculation  which  is  of 
value  as  showing  the  total  actual  work  accomplished. 
Usually  it  is  necessary  to  shut  down  the  house  at  least 
once  a  week  for  half  a  day  or  more  for  overhauling  the 
machinery,  and  particularly  for  cleaning  the  copper  heat- 
ing surfaces  of  the  evaporating  and  clarifying  apparatus. 
The  copper  becomes  badly  fouled  by  the  end  of  a  week 
from  the  deposits  from  the  juice,  necessitating  a  thorough 
cleaning,  usually  given  by  boiling  out  with  very  dilute 
hydrochloric  acid. 

At  the  time  of  shutting  down,  all  cane  and  thin  juices 
are  worked  up,  and  usually  all,  or  most,  of  the  meladura. 
The  first  sugars  are  worked  up,  except  what  may  be  repre- 
sented in  any  meladura  (and  in  some  cases  in  the  first 
molasses,  when  this  is  worked  into  the  first  boilings 
directly).  Hence,  pans  and  all  evaporating  and  clarifying 
apparatus  are  empty.  There  are  usually  many  tons  of 
second  sugars  in  process  which  must  be  estimated  before 
the  work  of  the  house  can  be  ascertained.  All  the  sugar 
represented  in  this  "stock  in  process"  is  carefully  calcu- 
lated, first,  by  determining  the  weight  of  the  different  prod- 
ucts from  their  densities  and  the  volume  of  the  containers, 
these  latter  being  among  the  constants  calculated  once  for 
all,  and  tabulated  in  the  laboratory  records.  From  the 
purity  figures  of  the  first  molasses  and  meladura,  similar 
calculation  constants  can  be  established,  by  which  the 
yield  of  sugars  from  the  stock  in  process  can  be  rapidly 
estimated. 


138  SUGARHOUSE   AND    REFINERY    METHODS 

From  the  amount  of  first  and  second  sugars  shown  to  be 
in  process  by  the  figures  of  the  "  stock  in  process"  book, 
must  be  deducted,  obviously,  the  corresponding  sugars 
held  in  process  at  the  end  of  the  previous  working  period. 

In  the  estimation  of  the  work  of  a  sugarhouse  during 
the  running  period,  from  one  clean-up  to  the  next,  the 
scheme  of  calculation  would  be  somewhat  as  follows : 

STOCK  WORKED  UP 

A.  Weight  of  cane  ground.     From  the  weighers'  books. 

B.  Weight  of  juice  extracted. 

Weighed  directly  by  automatic  scales,  or  determined 
from  number  of  defecators  of  known  volume,  in  gal- 
lons, which  can  be  expressed  in  pounds  by  equivalents 
calculated  on  the  Brix,  at  the  temperature  at  time  of 
gauging.  (Maceration  water  deducted  by  calculation, 
based  on  Brix  determinations  of  the  normal  and 
diluted  juice.) 

C.  Fibre  in  the  bagasse. 

D.  Weight  of  sugar  in  the  press  cake. 

Obtained  by  polarization  and  weight  of  total  cake ;  the 
latter  by  actual  weighing,  or  estimated  from  number 
of  presses  filled  and  calculated  weight  of  cake  per 
press. 

E.  Weight    of     first    sugar    manufactured.1     From    the 

weighers'  books. 

F.  Weight    of    second    sugar   manufactured.      From   the 

weighers'  books. 

1  If  the  second  sugars  are  remelted  and  worked  up  into  first  sugars,  allow- 
ance must  be  made  accordingly. 


SUGARHOUSE   AND   REFINERY   METHODS  139 

STOCK  IN  PROCESS 

G.    Weight  of  first  and  second  sugar  represented  in  the 

meladura  in  process. 

Calculated  from  the  number  of   gallons  in   tanks,  by 

equivalents  per  gallon,  based  on  the  purity  and  Brix. 

H.    Weight  of  second  sugar  represented  in  first  molasses. 

Calculated  from  gallons  in  tanks,  by  equivalents,  based 

on  the  Brix  and  purity  of  the  molasses. 
I.    Weight   of   second   sugar   represented   in   the   second 

massecuites,  in  cars  and  crystallizers. 
Calculated  from  weight  in  pounds  of  massecuites,  esti- 
mated from   volumes  of   containers  and  Brix,   using 
purity  equivalents. 
J.    Weight  of  sugar  in  second  molasses. 

Calculated  from    polarizations    and   first   molasses    and 
second  massecuites  in  process. 

From  the  above  data  are  obtained  the  following,  which 
are  expressed  either  as  percentages  of  sugar  on  the  weight 
of  cane,  or  on  the  weight  of  sugar  in  the  cane  : 

(1)  The  extraction  of  the  juice. 

(2)  The  sugar  in  the  cane. 

(3)  The  sugar  received  into  the  boiling  house. 

(4)  The  loss  of  sugar  in  the  bagasse. 

(5)  The  loss  of  sugar  in  the  filter-press  cake. 

(6)  The  yield  of  first  sugar. 

(7)  The  yield  of  second  sugar. 

(8)  The  loss  of  sugar  in  the  second  molasses. 

The  sum  of  the  percentages  of  yields  and  losses  will  not 
balance  the  per  cent  of  sugar  in  the  cane  by  .2-.4  per 
cent  of  the  weight  of  the  cane.  This  difference  is  known 


140  SUGARHOUSE  AND   REFINERY   METHODS 

as  "  undetermined  loss,"  and  may  be  possibly  due  to 
"chemical  losses/'  in  which  sugar  is  destroyed  by  inversion 
or  other  chemical  change  in 

(a)  Clarifying. 

(b)  Evaporating. 

(c)  Crystallizing. 

(d)  From  fermentation  in  tanks  and  other  apparatus. 

(e)  Chemical  changes  in  second  massecuites  from  fer- 
ments, molds,  or  obscure  chemical  changes. 

Or  "mechanical  losses"  from 

(f)  Entrain  men  t. 

(g)  Leaks  and  spills  from  accidents. 
(ft)   Losses  in  cleaning  out  apparatus. 

The  destruction  of  sugar  in  process  is  by  no  means  well 
understood.  Refinery  experiments  in  Europe  have  shown 
that  in  every  pan  boiling  ("  strike  ")  about  .4  per  cent  of 
the  sugar  is  destroyed.  Undoubtedly  some  chemical  loss 
occurs  in  the  evaporating  and  clarifying  processes.  To 
this  may  be  added  "apparent"  loss  due  to  errors  inherent 
in  polariscope  measurement,  which,  according  to  some 
authorities,  amount  to  some  tenths  of  a  per  cent. 

Fermentation  losses  in  any  part  of  the  house  under 
ordinary  conditions  of  work  are  inexcusable.  Absolute 
cleanliness  and  a  free  use  of  lime  and  steam  in  spots  liable 
to  infection  should  eliminate  this  trouble  in  a  properly 
designed  sugarhouse. * 

1  In  Louisiana  sugarhouses  certain  bacterial  organisms,  notably  leuconostoc 
mesenterioides,  have  destroyed  much  wagon  sugar,  transforming  the  sucrose 
into  dextran,  a  pentose  gum  which  is  a  close  analogue  of  dextrin. 

In  Porto  Rico,  the  writer  has  observed  leuconostoc  in  one  or  two  instances 
in  the  raw  juice  tanks,  where,  in  a  few  hours,  it  has  grown  enough  to  com- 
pletely clog  the  juice  pumps.  The  growth  was  easily  removed  and  did  not 
return.  Leuconostoc  seems  to  be  a  characteristic  of  unripe  canes. 


SUGARHOUSE   AND   REFINERY   METHODS  14! 

Some  mechanical  losses  will  occur,  necessarily  in  clean- 
ing, but  they  can  be  largely  controlled  by  good  manage- 
ment, provided  the  house  is  working  uniformly.  Frequent 
stoppages  necessarily  increase  these  losses. 

All  tanks  and  other  containers  should  be  numbered,  and 
an  accurate  record  of  their  volumes  be  kept.  Tank  vol- 
umes are  most  easily  figured  by  measuring  in  gallons  per 
inch  of  depth  of  liquor.  The  total  amount  of  liquor  in  a 
tank  can  then  be  quickly  calculated  by  gauging  with  a 
measuring  rod  and  multiplying  by  the  factor  giving  gallons 
per  inch  for  that  tank.  Defecators  and  other  apparatus 
with  irregular  bottoms  or  containing  coils  can  be  conven- 
iently calibrated  by  filling  the  irregular  section  with  water, 
and  dropping  the  contents  into  a  tank  of  known  capacity. 

The  above  rough  outline  of  a  scheme  of  control  for  the 
yields  and  losses  of  a  West  Indian  sugarhouse  is  only 
suggestive  of  the  way  such  work  is  done.  The  details 
may  vary  much  with  the  working  of  the  house  and  the 
facilities  given  the  chemist,  and,  as  already  said  in  the 
opening  of  the  chapter,  fundamental  principles  should  be 
mastered  rather  than  that  details  of  methods  in  any  par- 
ticular sugarhouse  should  be  copied,  as  the  chemist  must 
design  his  own  scheme  of  control  to  fit  the  peculiar  re- 
quirements of  his  house  and  the  time  and  facilities  at  his 
disposal. 

It  hardly  need  be  said  that  the  whole  scheme  of 
chemical  control  is  absolutely  dependent  on  the  accuracy 
of  the  sampling.  Too  little  attention  is  paid  to  this  in 
many  houses.  Obviously,  the  chemist  cannot  personally 
take  every  sample  himself  where  the  house  is  running 
continually  night  and  day.  Men  in  charge  of  sampling 


142  SUGARHOUSE  AND   REFINERY   METHODS 

should  be  trustworthy  and  intelligent,  for  negligence  and 
incompetence  here  cannot  be  made  good  by  the  most  care- 
ful laboratory  work.  In  Europe,  in  the  beet-sugar  houses, 
there  is  a  much  better  realization  of  the  importance  of  the 
sampling,  and  elaborate  registering  and  sampling  apparatus 
is  in  use  much  more  generally.  That  such  apparatus  is 
profitable  seems  unquestionable. 

Beside  the  measurements  and  determinations  which  have 
reference  to  the  accurate  estimation  of  the  work  of  the 
house,  there  are  others  which  are  valuable  for  the  control 
of  the  daily  factory  operations.  Some  of  the  laboratory 
determinations  for  this  purpose  have  already  been  dis- 
cussed, such  as  acidity  tests,  density  determinations  of  the 
meladura,  etc. ;  but  aside  from  these  there  are  daily  records 
kept  for  a  definite  twenty-four-hour  period,  starting  at  some 
fixed  hour,  say  from  six  o'clock  in  the  evening  of  one  day 
to  the  same  hour  of  the  next.  These  figures  are  mainly  of 
value  in  determining  the  efficiency  of  the  various  apparatus, 
as  well  as  the  sugarhouse  as  a  whole,  by  giving  the  rate 
at  which  the  product  is  worked  up.  Such  figures  are,  for 
instance,  bulletins  of  the  starting  and  stopping  of  the  mills, 
and  of  the  number  of  defecators,1  filter  presses,  crystallizers, 
etc.,  filled  and  emptied.  These  records,  kept  conspicuously 
placed  for  quick  inspection,  show  at  once  the  work  of  the 
house  from  hour  to  hour  as  well  as  for  the  complete  day\» 
run.  At  the  end  of  the  twenty-four-hour  period  these 
should  be  recorded  in  the  laboratory  books. 

1  One  large  Cuban  sugarhouse  has  recently  installed  a  watchman's  clock 
system  for  electrically  recording  the  defecator  tallies.  Numbered  magneto 
call-boxes  are  placed  at  each  defecator,  from  which  workmen  send  signals 
which  are  recorded  on  the  dial  of  a  watchman's  clock  as  each  defecator 
is  filled. 


SUGARHOUSE  AND   REFINERY   METHODS  143 

The  best  records  of  the  work  of  the  vacuum  pans  are 
made  by  recording  vacuum-gauges.  These  give  a  continu- 
ous plot  of  the  gauge  readings  during  the  whole  twenty- 
four-hour  period,  so  that  the  work  of  the  pan  is  known 
at  any  hour  of  the  day  or  night,  within  errors  of  a  few 
minutes. 

These  curves  have  been  found  to  be  of  great  value,  as 
they  give  permanent  records  of  (i)  the  exact  time  the  boil- 
ing is  started ;  (2)  the  length  and  efficiency  of  the  evapora- 
tion previous  to  graining  ;  (3)  the  time  the  graining  begins ; 
(4)  the  length  of  the  finishing  period;  (5)  the  exact  time 
the  strike  is  "  dropped  " ;  (6)  the  length  of  time  that  the 
pan  is  idle,  which,  in  molasses-sugar  strikes,  is  a  measure 
of  the  time  taken  in  filling  wagons  or  crystallizers.  Much 
other  instructive  information  is  often  obtained  from  the 
gauge  charts,  such  as  the  time  and  extent  of  irregularities 
in  working  of  the  condensing  apparatus,  etc.  In  connec- 
tion with  these  records,  those  taken  by  recording  gauges 
of  the  "live  "  and  "  exhaust "  steam  pressure  are  important, 
as  they  give  data  which  are  legitimately  in  the  province  of 
chemical  control,  and  explain  many  irregularities  in  the 
work  of  the  house  which  otherwise  are  interpreted  by  mere 
guess. 

Such  gauges  should  be  placed  in  the  laboratory  or  other 
office  where  they  can  be  cared  for.  The  greatest  care 
should  also  be  exercised  in  the  installation  of  the  connect- 
ing piping  to  avoid  leaks  and  to  insure  the  proper  trapping 
of  condensed  vapor.  If  these  precautions  are  not  carried 
out,  and  such  apparatus  treated  with  the  same  care  as  any 
other  instruments  of  high  precision,  it  is  worse  than  useless 
to  install  it. 


144  SUGARHOUSE   AND   REFINERY   METHODS 

In 'most  first-class  cane  sugarhouses  the  chemist  is  the 
superintendent  of  sugar  manufacturing,  as  he  should  be. 

Beet-sugar  Manufacture.  —  The  conditions  governing 
beet-sugar  manufacture,  as  well  as  the  chemical  differences 
between  beet  and  cane  juices,  have  resulted  in  making  it 
radically  different  from  cane-sugar  manufacture  in  many 
details  of  process.  In  this  country  at  least,1  refined  sugar 
is  made  directly  from  the  beet,  and  the  extraction  is  uni- 
versally by  "  diffusion,"  the  extracted  pulp  being  useless 
for  fuel,  but  a  valuable  food  for  cattle.  As  beet  sugar  is 
manufactured  in  regions  where  fuel  is  comparatively  cheap 
and  water  is  abundant,  the  diffusion  process  can  be  used 
to  great  advantage. 

As  beets  are  not  only  bought  by  the  sugarhouse,  but 
also  selected  with  great  care  for  seed  on  tests  mainly  based 
on  their  polarization,  beet  testing  is  one  of  the  most  im- 
portant and  extensive  operations  of  the  factory  laboratory. 
By  this  method  of  careful  seed  selection,  the  sugar  content 
of  the  beet  crop  as  a  whole  has  been  more  than  doubled  in 
the  past  century. 

In  a  large  establishment,  in  seed  testing  particularly, 
often  several  thousand  polarizations  have  to  be  made  in 
a  day.  Much  ingenious  and  labor-saving  apparatus  has 
been  especially  designed  to  meet  the  requirements  of  this 
great  volume  of  work.  Probably  no  industry  has  had  its 
technology  and  special  analytical  methods  more  thoroughly 
exploited  by  eminent  authorities  than  beet-sugar  manu- 
facture. The  reader  is,  therefore,  referred  to  the  works 

1  In  many  countries,  raw  cane  sugars  are  directly  consumed  as  food.  In 
fact,  such  sugars  were  common  in  our  own  groceries  a  generation  ago.  Raw 
beet  sugars,  on  the  contrary,  are  quite  unfit  for  food,  owing  to  their  vile  taste. 


SUGARHOUSE  AND   REFINERY   METHODS  145 

of  Stohmann,  Friihling,  Claassen,  Sidersky,  Spencer,  and 
others  for  details  of  these  processes  and  methods. 

Diffusion.  —  In  this  process  the  beets,  in  a  finely  chipped 
or  sliced  state,  are  subjected  to  the  action  of  hot  water. 
It  can  be  considered  as  a  kind  of  lixiviation  process,  but  is 
to  a  considerable  degree  a  clarification  process  as  well, 
as  the  hot  water  tends  to  coagulate  the  albuminoids  in  the 
plant  tissues.  These  matters  are  retained,  together  with 
other  colloidal  substances,  by  the  cell  membranes,  which 
allow  the  sugar  and  salts  -to  diffuse  freely  through.  The 
beets,  usually  brought  to  the  factory  by  small  flumes  of 
swiftly  running  water,  are  passed  into  a  washer  and  then 
to  the  "  cutters,"  where  they  are  reduced  by  notched  knives 
on  a  rapidly  revolving  wheel  to  a  form  resembling  French 
fried  potatoes.  These  "chips"  ("cosettes")  are  fed  into 
the  "diffusion  battery,"  consisting  of  ten  or  fifteen  tall 
cylindrical  (closed)  iron  tanks  ("cells"),  holding  ten  tons 
or  more.  These  tanks  are  constructed  to  carry  a  moderate 
pressure  and  arranged  so  that  the  liquors  can  be  passed 
from  one  to  the  other.  The  hot  water,  about  equal  in 
weight  to  the  chips,  is  allowed  to  stand  on  the  chips  in 
a  "  cell "  for  twenty  minutes  or  so,  and  then  is  passed  to 
the  next  cell.  When  the  battery  is  in  operation,  it  is 
usually  run  so  that  all  the  cells  are  full  except  two,  one 
which  is  filling,  the  other  dumping.  The  diffusate,  before 
leaving  the  battery,  finally  passes  over  at  least  one  cell  of 
fresh  chips,  and  the  work  is  commonly  so  arranged  that 
it  is  the  second  diffusate  of  the  three  previous  ones.  Dif- 
fusion gives  more  extraction  and  a  purer  juice  than  any 
milling  process,  but  dilutes  the  juice  15  or  20  per  cent. 
The  exhausted  chips,  after  the  excess  of  water  is  removed 


146  SUGARHOUSE   AND    REFINERY    METHODS 

by  a  specially  designed  press,  are  fed  to  live  stock,  the 
surplus  being  stored  in  covered  trenches  by  a  process  of 
ensilage. 

Clarification.  —  This  differs  radically  from  cane-sugar 
clarification,  being  much  more  elaborate  than  the  former. 
This  fact  is  chiefly  due  to  the  larger  amount  of  albuminoids 
in  beet  juices  and  the  greater  difficulty  of  removing  them, 
and  also  is  a  result  of  the  conditions  of  manufacture 
already  alluded  to  which  favor  the  manufacture  of  refined 
sugar.  The  process  is  known  as  the  "  carbonatation " 
method,  and  in  its  essentials  consists  in  treating  the  juice 
with  a  large  excess  of  lime  (about  2  per  cent,  although  3 
per  cent  or  more  is  often  used)  heating  to  80°,  and  then 
precipitating  the  lime  and  coagulated  albuminoids  with 
carbon  dioxide,  which  also  decomposes  the  calcium  sucrate 
formed.1  The  juice  is  then  passed  through  "bag  filters" 
or  filter  presses.  In  this  first  carbonatation,  the  process 
is  not  complete,  the  juice  being  still  somewhat  alkaline. 
It  is  now  treated  with  sulphur  dioxide,  and  again  with 
carbon  dioxide  till  practically  neutral,  and  the  slight  pre- 
cipitate formed  removed  by  "mechanical"  filters,  which 
are  small  closed  tanks  holding  thirty  or  more  flat  bags 
stretched  on  wire  frames.  The  juice  filters  from  outside 
into  the  bags,  and  passes  out  by  pipe  connections  in  the 
frames. 

A  further  treatment  of  the  concentrated  sirups  with 
sulphur  dioxide  is  usually  given.  The  lime  necessary  for 
clarification  is  made  at  the  factory  by  burning  limestone  in 
immense  iron  kilns  similar  in  shape  to  blast  furnaces, 

1  Carbonatation  in  modified  form  has  been  introduced  in  Java  cane-sugar 
houses,  but  its  advantages  are  questionable  in  raw  cane-sugar  manufacture. 


SUGARHOUSE  AND   REFINERY   METHODS  147 

so  arranged  that  the  carbon  dioxide  can  be  collected  and 
pumped  into  the  carbonatation  tanks. 

The  carbonatation  process  is  possible  in  beet  clarifica- 
tion, owing  to  the  absence  of  glucose  sugars,  for,  as  already 
stated,  these  are  decomposed  by  excess  of  lime  into  slimy 
humus  products  which  are  hard  to  remove,  and  also  give  a 
brown  (caramel)  color  to  the  sugar,  very  difficult  to  bleach. 
Normal  beets  are  practically  free  from  glucose  sugars,  but, 
in  American  practice,  beets  often  have  to  be  worked  up 
which  from  various  causes  (unripeness,  freezing,  etc.)  do 
contain  considerable  quantities  of  glucose. 

Such  beets  require  modification  of  the  carbonatation  pro- 
cess to  be  worked  successfully,  the  heating  of  the  alkaline 
solutions  being  reduced  as  far  as  practicable,  as  well  as 
the  amount  and  duration  of  the  alkaline  state,  while  sulphur 
dioxide  is  used  more  freely  to  keep  the  clarified  liquors 
neutral  or  even  faintly  acid. 

The  evaporation  and  crystallizing  processes  are  identical 
with  those  of  cane-sugar  manufacture ;  so  too,  in  its  essen- 
tials, the  centrifugal  purging,  the  washing  process  during 
the  purging  being  an  important  feature,  as  the  sugar  is 
turned  out  white.  Subsequently,  the  sugar  is  passed 
through  a  "granulator,"  a  long,  slowly  revolving,  nearly 
horizontal  drum,  heated  by  a  second  internal  steam  drum. 
The  sugar,  which  comes  from  the  centrifugals  with  about 
2.5  per  cent  of  moisture,  is  thoroughly  tossed  about  in  the 
granulator,  and  perfectly  dried,  emerging  as  the  "  granu- 
lated sugar"  of  the  grocer,  and  practically  indistinguish- 
able from  the  refinery  product.1 

1  Beet  sugars  refined  in  this  manner  do  not  hold  their  color  quite  as  well  as 
the  bone-black  refined  product.  On  long  standing,  they  gradually  assume  a 
slight  yellow  tint. 


148  SUGARHOUSE   AND   REFINERY   METHODS 

Second  sugars,  and  occasionally  thirds,  are  made  from 
the  purer  sirups  from  the  washing  of  the  first  sugars,  being 
usually  grained  in  crystallizers.  The  beet  molasses  (from 
normal  beets)  differs  radically  in  many  important  charac- 
teristics from  cane  molasses.  It  has  about  80  per  cent 
of  solids  and  averages  about  50  per  cent  of  sucrose,  10  per 
cent  of  ash,  and  20  per  cent  of  organic  "  non-sugar,"  largely 
nitrogenous,  consisting  of  albuminoids  and  decomposition 
products  of  albuminoids.  More  than  half  of  the  mineral 
matter  is  potassium  in  combination  with  organic  acids 
which  are  strongly  melassagenic.  This  means  that  these 
bodies  by  their  presence  prevent  the  sugar  from  crystalliz- 
ing, so  that  it  is  practically  impossible  to  extract  it  by 
further  boiling  or  ordinary  methods  of  clarifying. 

Many  ingenious  processes  have  been  devised  for  extract- 
ing this  sugar  from  the  beet  molasses.  One  which  is 
quite  often  used  is  osmosis,  in  which  the  hot  diluted  mo- 
lasses is  made  to  flow  through  an  "  osmogene,"  very  similar 
in  appearance  to  a  filter  press,  but  composed  of  pairs  of 
cells  separated  from  each  other  by  partitions  made  of 
parchment  paper.  Hot  water  flows  on  one  side  of  the 
partition,  the  dilute  molasses  on  the  other.  Many  of  the 
more  soluble  potash  and  other  salts  diffuse  more  rapidly 
than  the  sugar.  By  regulating  the  flow  and  temperature, 
sufficient  melassagenic  material  of  this  nature  can  be  re- 
moved, so  that  the  molasses,  on  boiling  in  the  vacuum  pan 
and  treatment  with  crystallizers,  is  said  to  yield  some  12 
per  cent  of  its  sugar.  By  further  treatment  of  the  mo- 
lasses from  the  osmose  sugar  by  a  second  osmosis  and 
boiling,  it  is  stated  by  Stohmann  that  12  per  cent  of  its 
sugar  can  again  be  obtained. 


SUGARHOUSE   AND   REFINERY   METHODS  149 

Another  method  of  extracting  sugar  from  beet  molasses, 
which  is  used  considerably,  is  known  as  Stefferis  pro- 
cess. In  this  the  diluted  molasses  is  treated  with  lime 
till  the  sugar  is  converted  into  monocalcium  sucrate,  and 
into  this  solution  is  put  fresh-burnt  lime  in  very  small  por- 
tions at  a  time,  while  the  temperature  is  kept  at  15°  C.  by 
a  cooling  apparatus.  In  this  way,  finally,  all  the  sugar  is 
precipitated  as  a  tricalcic  sucrate,  which  can  be  filtered  in 
filter  presses,  washed,  and  worked  back  into  the  juice,  being 
substituted  for  lime  in  the  carbonatation  process.  Stron- 
tium and  barium  hydrates  have  been  substituted  for  lime 
in  similar  processes.  The  only  impurity  which  is  carried 
along  with  the  sugar  in  this  process  is  raffinose. 

It  will  be  seen  from  the  above  outline  of  beet-sugar 
factory  methods  that  the  scheme  of  chemical  control 
will  differ  considerably  from  that  of  the  cane-sugar  house. 
Reference  has  already  been  made  to  the  analysis  of  beets 
for  seed  and  for  establishing  the  purchase  price,  there 
being  no  difficulty  in  obtaining  a  representative  sample, 
as  in  the  case  of  cane.  The  usual  method  of  obtaining  the 
sample  is  by  making  a  boring  with  a  cylindrical  rasp  through 
the  beet  diagonally  in  a  direction  which  experiment  has 
shown  to  give  a  section  representative  of  the  average  beet 
contents.  The  rasp  is  made  to  revolve  very  rapidly,  and  is 
so  constructed  that  the  raspings  are  retained  in  the  hollow 
cylinder  of  the  tool.  In  other  rasps  a  wedge-shaped  section 
is  cut  out  of  the  beet,  and  drops  into  a  metallic  box. 

Determination  of  Sugar  in  Beets.  —  The  usual  way  is 
by  the  "hot  digestion"  method.  The  normal  weight  of 
pulp  is  washed  into  a  funnel-mouthed  flask,  graduated  to 
hold  201.35  cubic  centimeters,  the  1.35  cubic  centimeters 


I  $0  SUGARHOUSE  AND   REFINERY   METHODS 

being  the  allowance  for  the  "marc"  or  pulp  and  the  vol- 
ume of  the  precipitate,  5  to  7  cubic  centimeters  of  a  basic 
lead  acetate  solution  of  a  density  of  1.25  having  been  pre- 
viously run  into  the  flask.  The  contents  of  the  flask  are 
nearly  made  up  to  the  mark  with  water,  and  heated  on  a 
water  bath  for  30  minutes  at  80°  C.  after  thorough  shaking 
and  the  addition  of  a  drop  or  two  of  ether  to  dispel  the 
foam.  It  is  then  acidulated  with  acetic  acid  and  made  up 
to  the  mark  after  cooling.  The  polarization  is  made  in  a 
4-decimeter  tube  when  practicable,  to  avoid  doubling  the 
reading.  If  a  2OO-cubic-centimeter  flask  is  used,  the 
weight  of  the  pulp  taken  is  25.87  grams,  instead  of 
26.048. 

The  analysis  of  the  juice  is  made  by  the  "  indirect " 
method.  The  beet  is  cut  up  into  small  pieces  and  put 
through  a  screw  fruit  press,  or,  much  better,  rasped,  and 
pressed  in  a  very  powerful  laboratory  press  made  for  the 
purpose.  The  polarization  and  purity  tests  are  made  as 
for  cane  juices.  The  per  cent  of  sugar  in  the  beet  is 
often  calculated  from  the  juice  polarization  by  taking  the 
arbitrary  factor  .95. 

Ash  Determination.  —  The  methods  of  analysis  of  the 
diffusion  juice  are  practically  the  same  as  for  cane  juices, 
but  as  the  mineral  matter  plays  such  a  large  part  in  caus- 
ing manufacturing  losses,  owing  to  its  comparatively  large 
amount  and  its  strongly  melassagenic  action,  its  estimation 
is  important.  This  is  done  by  a  determination  of  the  ash 
of  the  juice.  The  ordinary  method  of  making  an  ash 
determination  of  a  saccharine  solution  is  to  dry  10  grams 
in  a  platinum  dish,  on  a  water  bath,  and  then  burn  off  the 
organic  matter  in  a  "  low  temperature "  muffle,  which  is 


SUGARHOUSE  AND   REFINERY   METHODS  151 

kept  at  a  dull  red  heat,  not  over  750°  C.  The  organic 
matter  is  rapidly  consumed  at  this  temperature,  which  is 
not  sufficient  to  volatilize  the  chlorides.  Several  methods 
have  been  devised  for  overcoming  the  difficulty  of  the 
excessive  swelling  of  the  carbonized  mass  in  the  prelimi- 
nary stages  of  the  burning,  which  is  characteristic  of  carbo- 
hydrate substances.  A  very  small  lump  of  vaseline  put  in 
the  dish  before  igniting  works  very  well.  In  beet  products,1 
however,  it  is  customary  to  use  Scheibler's  method,  and 
add  a  few  drops  of  concentrated  sulphuric  acid,  just  suffi- 
cient to  moisten  the  dried  residue,  which  will  then  burn 
without  making  a  bulky  coal  in  the  preliminary  stages. 
The  "sulphated  ash,"  as  it  is  called,  obviously  is  heavier 
than  would  be  an  untreated  ash,  owing  to  the  higher  mo- 
lecular weight  of  the  sulphuric  radical.  Scheibler  found 
that  in  beet  products  a  deduction  of  one  tenth  from  the 
weight  of  the  sulphated  ash  gave  the  equivalent  of  the 
normal  ash.  The  per  cent  of  sugar  divided  by  the  per  cent 
of  ash  in  a  beet  product  is  known  as  the  "  saline  coeffi- 
cient," and  is  an  instructive  figure  to  the  beet-sugar 
manufacturer.  Good  beets  give  a  coefficient  of  20  or 
over. 

Manufacturing  Loss.  —  The  first  loss  is  in  the  diffusion 
chips  and  in  the  wash  water  expressed  from  the  chips  by 
the  chip  press.  This  approximates  about  .4  per  cent  on 
the  weight  of  the  beets. 

The  next  losses  occur  in  the  carbonatation  scums,  which 
are  polarized  as  described  for  cane-juice  filter  cake,  except 
that  care  must  be  taken  always  to  acidulate  the  solution 

1  Ash  determinations  should  be  made  on  the  filtered  solutions  in  case  of 
raw  sugars  which  contain  sand  and  other  foreign  matter. 


152  SUGARHOUSE  AND   REFINERY   METHODS 

with  acetic  acid  to  decompose  the  lime  sucrates  present  in 
the  beet  filter  cake.  A  further  loss  occurs  in  the  mechani- 
cal filtrations  of  the  sirups,  averaging  .05  per  cent.  The 
chemical  and  other  mechanical  losses,  which  are  those 
which  have  been  enumerated  under  cane-sugar  manufac- 
ture, bring  the  actual  total  losses  to  an  average  of  about 
i  per  cent,  although  they  figure  .4  per  cent  or  more 
larger,  a  result  due,  according  to  some  authorities,  to  errors 
of  polarizations,  which  are  usually  additive. 

Quotient  of  Purity  Tests  of  Beet  Products.  —  The  method 
of  determining  quotient  of  purity  described  for  cane  juices, 
in  which  the  total  solids  is  assumed  to  be  given  by  the 
Brix  reading,  invariably  gives  too  low  results,  owing  to  the 
large  amount  of  mineral  matter  present,  which  has  an 
influence  on  the  density  over  twice  as  great  as  that  of 
sugar.  A  solution  of  calcium  chloride  of  I  per  cent,  for 
instance,  would  read  nearly  2.5°  Brix.  Hence,  it  is 
necessary  for  accurate  work  to  obtain  the  total  solids 
by  drying. 

Drying  of  Saccharine  Products.  —  It  is  very  difficult  to 
determine  moisture  accurately  in  sirups  and  other  solu- 
tions of  sugar,  because  as  the  drying  proceeds,  an  im- 
pervious varnish  of  the  saccharine  material  forms  over 
the  surface,  which  confines  the  moisture  of  the  lower 
layers.  For  satisfactory  drying,  the  solution  during  dry- 
ing must  be  distributed  in  very  thin  films  over  a  large 
surface.  This  is  done  most  effectively  by  diluting  the 
substance  to  a  thin  sirup  and  pouring  it  over  clean  sand 
or  pumice  stone,  and  then  evaporating  at  a  temperature  of 
105°  C.  in  a  hot-air  oven,  till  a  practically  constant  weight 
is  obtained,  — practically  constant,  because  the  drying  is 


SUGARHOUSE   AND    REFINERY    METHODS  153 

beset  with  another  difficulty,  the  gradual  increase  in  weight 
due  to  the  oxidation  of  the  sugar,  which  takes  place  rapidly 
in  the  dried  product  at  the  air-bath  temperature.  The 
usual  method  of  determining  the  point  of  dryness  is 
when  the  loss  in  weight  does  not  exceed  .2  per  cent 
per  hour.1 

This  oxidation  error  is  mitigated  by  drying  in  a  vacuum 
at  70°  C.  Lobry  de  Bruyn  and  Van  Laent 2  have  used  a 
vacuum  apparatus  arranged  so  that  in  the  final  stages  of 
drying  the  vapors  are  passed  over  phosphorus  pentoxide. 
Brown,  Morris,  and  Millar  have  dried  most  of  the  common 
carbohydrates  with  this  apparatus,  and  determined  their 
density  influences  per  gram  in  100  cubic  centimeters  for  all 
concentrations  up  to  about  25  per  cent.  This  apparatus 
is  somewhat  complicated  and  the  process  tedious  for  com- 
mercial work.  The  method  almost  universally  used  in 
refineries  and  sugarhouses  is  drying  in  the  hot-air  bath 
at  105°. 

Weisberg  has  worked  up  a  table  of  coefficients  for  trans- 
forming "apparent  quotients  "  (those  obtained  by  the  Brix 
spindle)  into  true  values.  It  is  said  to  give  correct  results 
when  the  solution  of  the  beet  product  is  made  up  to  the 
normal  (saccharimeter)  concentration  of  26.048  grams  in 
100  Mohr  cubic  centimeters.  Usually  two  or  three  times 
the  normal  weight  is  taken  in  the  corresponding  volume  to 
allow  of  sufficient  solution  for  the  Brix  determination.  The 
following  is  the  table  of  Weisberg : 

1  The  United  States  Custom  House  method  for  determination  of  moisture 
in  molasses  and  sirups  is  to  spread  I  to  2  grams  over  the  bottom  of  a  flat  dish 
at  least  7  centimeters  diameter,  and  dry  for  two  hours  at  100°  C. 

2  Rec.  Trav.  Chim.,  13,  218. 


154 


SUGARHOUSE  AND  REFINERY  METHODS 


APPARENT  QUOTIENT 

COEFFICIENT 

APPARENT  QUOTIENT 

COEFFICIENT 

57.0 

.054 

79.0 

.O2O 

57-5 

.052 

8o.O 

.019 

58.0 

.050 

81.0 

.018 

59.0 

.046 

82.0 

.017 

60.0 

.044 

83.0 

.Ol6 

61.0 

.042 

84.0 

.015 

62.0 

.040 

85.0 

.014 

63.0 

.038 

86.0 

.013 

64.0 

.036 

87.0 

.012 

65.0 

•034 

88.0 

.Oil 

66.0 

•033 

89.0 

.OIO 

67.0 

.032 

90.0 

.009 

68.0 

.031 

91.0 

.008 

69.0 

.030 

92.0 

.007 

70.0 

.029 

93-o 

.OO6 

71.0 

.028 

94.0 

.005 

72.0 

.027 

95  -o 

.OO4 

73-o 

.026 

96.0 

.003 

74.0 

.025 

97.0 

.002 

75.0 

.024 

98.0 

.OO2 

76.0 

.023 

99.0 

.OOI 

77.0 

.022 

IOO.O 

.OOO 

78.0 

.O2I 

Weisberg's  method  is  particularly  adapted  for  determin- 
ing the  quotient  of  purity  of  massecuites. 

The  chemical  determinations  necessary  for  controlling 
the  daily  work  of  the  beet-sugar  house  are  evidently  much 
more  various  than  those  of  cane-sugar  manufacture,  and 
comprise  analyses  of  the  limestones  used  in  the  kiln,  as 
well  as  the  lime  itself,  the  kiln  gases  used  in  carbonatation, 
alkalinity  tests  of  the  juices  and  sirups  in  process,  besides 
occasional  analyses  of  fuel,  boiler  deposits,  fertilizers,  etc. 


SUGARHOUSE  AND   REFINERY   METHODS  155 

Moreover,  there  is  much  chemical  work  which  could  be 
done  to  advantage,  both  in  cane  and  beet  sugar  laborato- 
ries, not  only  directly  bearing  on  the  work  of  the  factory, 
but  in  research  work  on  problems  constantly  arising.  How- 
ever, very  few  factory  laboratories  have  the  facilities  for 
more  than  the  necessary  routine  control  work. 

Refinery  Methods.  —  The  refinery  takes  raw  sugars  of 
all  sorts,  the  great  bulk  of  which  is  turned  into  a  product 
which  is  practically  chemically  pure  white  sugar,  mostly  in 
granulated  form,  although  considerable  is  manufactured 
into  the  various  forms  of  "  lump  "  or  "loaf"  sugar,  and 
moist  "  yellow  "  sugars. 

As  has  already  been  explained,  raw  sugar  reaches  the 
refinery  in  many  forms  and  qualities.  There  are,  however, 
practically  four  classes  of  sugars  which  are  recognized : 
(i)  first  centrifugal  cane  sugars,  (2)  second,  or  molasses, 
and  muscovado  sugars,  (3)  beet  sugars,  corresponding  to 
cane  first  sugars,  (4)  "  jaggerys  "  and  other  crude  products 
of  primitive  manufacture. 

With  the  exception  of  beet  sugar,  the  price  of  the  sugars 
in  each  class  is  directly  fixed  by  the  polarization.  In  valu- 
ing beet  sugars,  the  amount  of  mineral  matter  (ash)  is  also 
taken  into  consideration,  as  this  is  largely  a  constituent  of 
melassagenic  salts.  The  custom  is  to  subtract  five  times 
the  ash  per  cent  from  the  polarization  in  valuing  the  sugar. 
For  instance,  a  beet  sugar  polarizing  96  per  cent  with 
an  ash  of  1.25  per  cent  would  be  rated  as  a  cane  sugar 
polarizing  89.75  per  cent.  This  is  based  on  actual  results 
obtained  in  European  refinery  practice,  but  is  said  by  some 
authorities  not  to  apply  except  to  what  are  known  as 
"export  sugars,'*  the  only  kind  of  raw  beet  sugar  which 


156  SUGARHOUSE   AND    REFINERY   METHODS 

reaches  the  United  States.  The  ash  of  the  lower  grade 
cane  sugars  is  also  often  determined  in  order  to  classify 
them. 

The  better  grade  of  raw  sugars  are  at  once  washed  in 
large  centrifugal  machines,  by  which  90  per  cent  or  more 
is  separated  as  crystals  of  practically  white  sugar  of  a 
purity  of  about  99.5,  for  the  greater  part  of  the  impurities 
exist  as  a  coating  on  the  crystals,  and  so  can  be  collected 
in  the  wash  sirups. 

The  washed  sugar  is  dissolved  in  the  "  melters "  to 
a  sirup  of  about  30°  Beaume,  which  is  defecated  in  a 
manner  similar  to  that  used  in  raw-sugar  manufacture, 
although  other  coagulants  are  often  used  with  lime,  the 
suspended  solid  matters  customarily  being  removed  by 
passing  through  "bag  filters."  The  clear  sirups  are  then 
decolorized  by  bone  black  in  the  "  char  filters,"  and  the 
practically  colorless  sirups  boiled  in  vacuum  pans  and  the 
sugar  separated  and  washed  white  in  centrifugal  machines 
by  the  methods  already  described.  The  sugar  is  dried  in 
granulators,  and  is  ready  for  market  after  sifting  into 
different  grades  of  fineness  and  packing.  The  sirups 
from  the  preliminary  washing  of  the  raw  sugar  are  mixed 
with  the  "  meltings  "  of  the  lower  grade  sugars  and  sub- 
jected to  an  identical  process,  in  most  cases  precipitants 
being  used  with  the  lime  for  more  effective  clarification. 
Finally,  the  washings  from  the  bone-black  filters  and 
other  apparatus,  and  from  the  bag-filter  scums,  if  not 
utilized  in  the  melting,  are  concentrated  in  a  multiple- 
effect  evaporator,  and  worked  into  the  other  liquors.  The 
sirups  from  the  refined  sugars  are  reboiled  in  the  vacuum 
pan  for  sugar,  the  less  pure  ones  being  used  for  charging 


SUGARHOUSE   AND   REFINERY   METHODS  157 

after  the  grain  is  formed.  When  the  purity  of  the  sirups 
from  the  reboiling  falls  below  a  certain  value,  say  about 
84,  it  is  no  longer  profitable  to  boil  them  in  the  pan  without 
further  refining,  unless  to  make  soft  yellow  sugars.  These 
sirups  are  therefore  added  to  others  in  process  at  a  stage 
depending  on  their  purity,  or  boiled  to  low-grade  sugar, 
which  is  remelted.  In  fact,  practically  the  whole  work  of 
the  refinery  is  governed  by  the  purity  tests  of  the  liquors 
in  process,  by  which  is  determined  the  most  effective  way 
to  combine  the  different  lots  for  most  economical  refining. 
When  it  is  known  that  in  the  larger  refineries  1500  tons  or 
more  of  sugar  are  refined  daily,  it  will  be  readily  seen  that 
failure  to  take  advantage  of  the  most  effective  blending 
or  working  up  of  the  diverse  sirups  and  liquors  in  process 
may  mean  large  money  loss.  Finally,  when  the  purity  of 
the  sirups  put  constantly  back  in  process  in  different  ways 
falls  below  about  45  actual  purity,  it  is  no  longer  profitable 
to  re-work  them  for  sugar,  and  they  are  sold  as  "  barrel 
sirups"  (English,  " treacle")  for  use  as  food  sirups  or  in 
brewing. 

From  what  has  been  said  in  this  rough  outline  of  the 
complicated  process  of  refining,  it  will  be  evident  that, 
beside  the  polarization  of  the  raw  sugars  and  the  refined 
products,  the  determination  of  the  quotient  of  purity  of  the 
many  and  various  liquors  in  process  will  be  an  indispensa- 
ble function  of  the  laboratory ;  in  fact,  its  most  important 
work,  as  by  it  is  controlled  the  entire  arrangement  of  the 
refining  of  the  different  stock  in  process.  Perhaps  the 
next  most  important  routine  work  of  the  refinery  labora- 
tory is  the  control  of  the  bone-black  filtration.  Bone  black 
is  indispensable  as  a  decolorizer  in  sugar  refining.  It  is 


158  SUGARHOUSE  AND   REFINERY  METHODS 

one  of  the  greatest  items  of  cost,  as  the  material  is  expen- 
sive, requires  elaborate  machinery  for  its  handling,  and 
undergoes  considerable  loss  by  disintegration  in  treatment. 
About  a  pound  of  bone  black  is  required  per  pound  of 
sugar  decolorized.  After  bone  black  has  been  used  a  short 
time,  its  pores  become  clogged,  and  it  loses  its  decolorizing 
power.  It  is  then  washed  and  partially  dried  by  steam, 
passed  through  a  dryer,  heated  to  dull  redness  in  tubular 
retorts1  to  consume  the  organic  material  which  clogs  its 
pores,  and  finally  passed  through  revolving  screens  to 
remove  the  finer  disintegrated  part,  which  is  rejected  as 
"  spent  black/'  still  valuable  for  many  purposes,  from  the 
phosphate  it  contains.  New  black  often  has  to  undergo 
a  preliminary  treatment  with  dilute  acid  and  a  washing 
known  as  "tempering"  before  it  can  be  used.  If  the 
various  processes  of  "  revivifying  "  the  black  are  not  car- 
ried out  properly,  the  pores  of  the  revivified  black  become 
clogged  with  carbonaceous  and  mineral  matter,  to  the  great 
loss  of  its  efficiency.  Hence,  the  daily  condition  of  the 
black  must  be  closely  followed  by  the  chemist  by  analysis, 
particularly  determinations  of  the  carbon  and  lime  con- 
tent.2 The  amount  of  phosphate  is  also  important  as  a 
measure  of  the  durability  of  the  black. 

As  a  rule,  the  chemist  of  a  refinery  has  little  to  do  with 
:he  active  management  of  the  refinery,  or  in  fact  with  the 

1  Sometimes  the  bone  black  is  subjected  to  a  roasting  process  known  as 
*  decarbonizing."  This  volatilizes  considerable  of  the  organic  matter  clogging 
the  pores  of  the  black,  which  would  otherwise  be  deposited  as  carbon  in  its 
passage  through  the  retorts.  Formerly  the  bone  black  was  allowed  to  stand 
in  heaps  to  allow  this  organic  matter  to  be  destroyed  by  fermentation. 

2 For  methods  of  bone-black  analysis,  see  Tucker,  "Manual  of  Sugar 
Analysis." 


SUGARHOUSE  AND   REFINERY  METHODS  159 

calculation  of  yields  and  losses.  These  calculations  are  so 
extensive  and  complicated  that  they  are  usually  made  part 
of  the  bookkeeping  of  the  office  force,  under  direction  of 
the  superintendent  and  his  assistants,  the  laboratory  records 
being  practically  confined  to  the  actual  analytical  work. 

The  losses  in  a  refinery,  according  to  European  practice, 
are  said  to  be  .5  per  cent  mechanical  and  .55  per  cent 
chemical,  on  the  weight  of  the  raw  sugar  actually  refined. 


CHEMICAL    METHODS    OF    DETERMINING 
SUGARS 

ALL  the  common  glucose  and  saccharose  sugars,  with  the 
exception  of  sucrose,  exert  a  marked  reducing  action  when 
heated  with  alkaline  solutions  of  many  metallic  salts. 
This  behavior  is  characteristic  of  organic  compounds 
known  as  "  aldehydes  "  and  "  ketones,"  which  can  be  con- 
sidered as  partially  oxidized  from  hydrates  (alcohols)  and 
in  a  transition  state  between  the  latter  and  the  more  com- 
pletely oxidized  form  of  the  acid.  Consequently,  like  all 
readily  oxidizable  chemical  compounds,  they  are  strongly 
reducing  in  their  action.  All  the  sugars  are  known  to 
have  an  aldehyde  or  ketone  structure,  being  sometimes 
classified  as  "  aldoses  "  and  "ketoses." 

The  Fehling  Volumetric  Method.  —  In  1848  Fehling 
developed  a  practical  method  for  utilizing  this  reducing 
property  of  the  sugars  on  copper  salts  as  a  means  of  quan- 
titative determination  of  the  sugars  themselves.  Fehling 
used  a  strongly  alkaline  solution  of  copper  tartrate  for  his 
metallic  solution,  the  concentration  of  which  was  so  de- 
signed that  the  copper  salt  in  10  cubic  centimeters  of  this 
solution  would  be  completely  reduced  to  cuprous  oxide, 
when  boiled  with  .05  gram  of  dextrose,  under  the  condi- 
tions of  the  process. 

Fehling's  original  solution,  according  to  Wiley,  is  made 
as  follows :  34.64  grams  of  pure  crystallized  copper  sul- 

160 


CHEMICAL   METHODS   OF   DETERMINING   SUGARS       l6l 

phate  (free  from  efflorescence)  is  dissolved  in  a  small 
quantity  of  water  (less  than  300  cubic  centimeters),  and  90 
grams  of  sodium  hydroxide  is  also  dissolved  in  about  600 
cubic  centimeters  of  water  in  which  is  subsequently  dis- 
solved 150  grams  of  potassium  tartrate.  The  solutions 
are  then  mixed  and  made  up  to  1000  cubic  centimeters. 
Later,  173  grams  of  the  double  sodium-potassium  tartrate 
("  Rochelle  salt")  was  substituted  for  the  potassium  tar- 
trate. 

Nearly  thirty  modifications  of  Fehling's  original  solution 
have  been  made,  the  majority  of  which  vary  mainly  in  the 
amount  of  alkali  used.  Owing  to  the  fact  that  Fehling 
solutions  decompose  spontaneously  after  a  short  time  and 
precipitate  copper,  the  modern  formulae  are  for  two  solu- 
tions, one  containing  copper  sulphate,  the  other  alkaline 
tartrate.  If  the  copper  sulphate  solution  is  made  slightly 
acid  with  a  cubic  centimeter  of  sulphuric  acid  per  liter,  and 
both  solutions  kept  in  tightly  stoppered  bottles  of  good 
glass,  they  will  keep  indefinitely.  A  mixture  of  equal  vol- 
umes of  the  two  solutions  gives  the  Fehling  liquor. 
Soxhlet's  formula  is  as  follows  : 

Solution  No.  i.  —  Copper  sulphate  in  crystals,  69.28 
grams  in  1000  cubic  centimeters  of  water. 

Solution  No.  2.  —  Rochelle  salt,  346  grams  dissolved 
in  about  600  cubic  centimeters  of  water,  to  which 
is  then  added  100  grams  of  sodium  hydroxide  in 
200  cubic  centimeters  of  water.  Solution  made 
up  to  1000  cubic  centimeters. 

The  original  method  of  Fehling  is  a  volumetric  one,  and 
according  to  Sutton  is  as  follows  :  5  cubic  centimeters  of 

M 


1 62      CHEMICAL   METHODS   OF  DETERMINING   SUGARS 

each  solution  is  measured  into  a  small  porcelain  dish,  the 
resulting  10  cubic  centimeters  of  clear  deep  blue  Fehling 
liquor  diluted  with  40  cubic  centimeters  of  water  and 
quickly  heated  to  boiling.  The  sugar  solution  which 
must  be  at  a  concentration  of  about  .5  per  cent,  is  then 
run  in  from  a  burette  in  small  quantities  till  the  blue 
color  of  the  copper  just  disappears.  The  volume  of 
sugar  solution  added  to  decolorize  is  assumed  to  contain 
.05  gram  if  dextrose,  other  sugars  giving  different  reduc- 
tion weights. 

Unfortunately,  the  reduction  value  obtained  varies  con- 
siderably with  the  manipulation,  being  dependent  on  the 
length  of  boiling,  the  exposure  of  the  solution  to  the  oxi- 
dizing influence  of  the  air,  and  the  amount  of  sugar  present 
at  different  steps  in  the  titration.  Many  attempts  have 
been  made  to  improve  the  volumetric  process  so  as  to 
reduce  the  inherent  errors. 

None  of  these  improved  volumetric  methods  seem  to 
have  any  advantages  over  the  original  one  of  Fehling, 
when  the  following  conditions  are  observed,  these  being 
vital  for  accuracy,  whatever  the  method  used  : 

(i)  To  arrange  for  the  concentration  of  the  sugar  solu- 
tion, or  the  dilution  of  the  Fehling  liquor,  so  that  in  all 
determinations  the  volume  of  the  boiling  liquid  is  a  fixed 
one;  (2)  to  add  at  once  practically  all  the  sugar  solution 
necessary  to  decolorize  the  Fehling  liquor ;  (3)  to  carry 
out  the  test  under  as  uniform  an  air  exposure  as  possible, 
i.e.  in  flasks  of  uniform  size  and  shape;  (4)  to  boil  with 
the  Fehling  solution  uniformly  for  a  fixed  period.  The 
disappearance  of  the  copper  from  the  solution  by  precipi- 
tation can  be  determined  conveniently  by  spotting  a  drop 


CHEMICAL   METHODS   OF   DETERMINING   SUGARS       163 

on  a  tile  or  on  the  paper  prepared  for  the  purpose,  and 
testing  the  clear  portion  of  the  spot  with  potassium  ferro- 
cyanide  acidified  with  acetic  acid. 

Hence,  it  cannot  be  assumed,  except  in  very  rough 
work,  that  .05  gram  of  sugar  is  necessarily  the  exact 
amount  to  discharge  the  color  of  10  cubic  centimeters  of 
Fehling  liquor  under  the  conditions  of  analysis.  Each 
operator  should  determine  for  himself  what  the  reduction 
factor  is  as  he  personally  carries  out  the  test,  by  standard- 
izing the  Fehling  liquor  with  a  solution  of  pure  dextrose  or 
invert  sugar. 

Standard  Dextrose  Solution.  —  Chemically  pure  anhy- 
drous dextrose  can  be  obtained  of  the  dealers  in  pure 
chemicals.  It  is,  however,  best  to  recrystallize  in  pure 
alcohol  before  using.  The  principal  impurity  in  anhydrous 
dextrose  is  moisture,  and  as  the  sugar  is  troublesome  to 
dry,  the  better  way  is  to  prepare  an  approximately  10  per 
cent  solution,  and  determine  the  exact  amount  of  dextrose 
contained  by  means  of  the  density  taken  with  the  pyk- 
nometer.  The  density  factors  at  15.5°  C.,  referred  to  water 
at  15.5°  C.,  have  been  worked  out  with  great  exactness  by 
Brown,  Morris,  and  Millar.1  For  a  solution  of  approxi- 
mately 10  per  cent,  the  grams  of  dextrose  in  100  cubic 
centimeters  (Mohr,  15.5°)  are  given  by  the  following  equa- 
tion: w= =— ,  where  w  is  the  number  of  grams  in  100 

.003035 

cubic  centimeters  of  solution,  and  <^the  density.  Knowing 
the  concentration  of  the  dextrose  solution,  its  purity  can 
be  established  by  a  determination  of  its  specific  rotatory 

!/.  C/iem.  Soc.  (London),  1897,  71,  p.  73,  also  p.  275. 


1 64      CHEMICAL   METHODS   OF  DETERMINING   SUGARS 

power.1     [a]^  of  an  approximately  10  per  cent  solution  of 
dextrose  at  20°  C.  is  52.74  according  to  Landolt. 

Standard  Invert  Sugar  Solution.  —  According  to  Fruhling, 
this  is  made  as  follows  :  9.50  grams  of  pure  cane  sugar  are 
dissolved  in  75  cubic  centimeters  of  water  in  a  ico-cubic- 
centimeter  flask,  and  5  cubic  centimeters  of  hydrochloric 
acid  of  a  density  of  1.19  added,  and  the  whole  thoroughly 
mixed.  The  solution  is  then  heated  in  a  water  bath  kept 
at  a  temperature  of  70°,  the  flask  being  immersed  in  the 
water  up  to  its  neck.  The  solution  should  reach  the  bath 
temperature  in  from  2\  to  5  minutes,  and  the  heating 
should  be  continued  for  5  minutes  more. 

The  solution  is  then  cooled  to  the  room  temperature  and 
diluted  to  the  loo-cubic-centimeter  mark.  Fifty  cubic  cen- 
timeters of  this  solution,  corresponding  to  5  grams  of 
invert  sugar,  are  put  into  a  liter  flask,  carefully  neutralized 
with  sodium  carbonate,  and  made  up  to  the  mark.  This 
solution,  every  cubic  centimeter  of  which  contains  .005 
gram  of  invert  sugar,  is  used  to  standardize  the  Fehling 
solution. 

Theoretically,  in  the  volumetric  Fehling  reaction,'  one 
equivalent  of  dextrose,  of  a  molecular  weight  of  180, 
reduces  ten  equivalents  of  crystallized  copper,  sulphate 
(CuSO4  5  H2O)  of  a  total  molecular  weight  of  2494,  but 
actually,  at  the  same  time  as  the  sugar  is  being  oxidized 
the  action  of  the  alkali  present  is  to  break  up  the  sugai 
molecule  into  a  complex  mass  of  decomposition  products, 

1  Dextrose,  like  many  other  sugars  in  the  crystalline  state,  when  freshly 
dissolved  has  a  temporary  specific  rotation  which  gradually  changes  to  the 
normal  value  after  some  hours.  If  heated  to  boiling,  the  solution  at  once 
gives  the  normal  specific  rotation.  Hence,  the  solution  should  be  brought  to 
a  boil  and  cooled  before  polarizing.  This  phenomenon  will  be  discussed  later. 


CHEMICAL   METHODS   OF   DETERMINING   SUGARS       165 

salts  of  numerous  organic  acids.  As  already  noted,  the  air 
also  exerts  a  marked  oxidation. 

Many  attempts  have  been  made  to  devise  solutions 
doing  away  with  the  alkali,1  but  this  seems  essential.  Any 
decrease  in  quantity  of  the  alkali,  whether  potassium  or 
sodium  hydrate,  decreases  the  sensitiveness  of  the  Fehling 
solution  to  reduction.  Ammonia  has  been  substituted  for 
sodium  or  potassium,  in  part  or  whole,  by  Pavy  and  others, 
as  the  former  does  not  act  so  energetically  on  the  glucose 
molecule.  These  solutions  give  a  very  sharp  end  point,  as 
there  is  no  precipitate  of  cuprous  oxide  to  obscure  the 
solution,  and  are  valuable  in  cases  where  ammonium  or 
its  derivatives  are  already  present  in  the  solution,  but  are 
inconvenient,  owing  to  the  necessity  of  providing  for  a  uni- 
form ammonia  content  during  the  titration  and  the  exclu- 
sion of  air.  The  reader  is  referred  to  Wiley's  "  Principles 
and  Practice  of  Agricultural  Analysis,"  volume  III,  for 
a  more  extended  description  of  Fehling  and  similar 
methods. 

The  Fehling  volumetric  methods  are  much  used  in  sugar 
analysis,  owing  to  their  rapidity,  and  are  valuable  where 
small  quantities  of  invert  sugar  or  glucose  are  to  be 
determined  within  a  few  per  cent  of  their  value,  which 
is  usually  all  that  is  required  in  commercial  work,  but 
in  general  can  hardly  be  depended  on  for  more  accurate 
work.  When  greater  precision  is  required,  the  gravi- 
metric methods  are  necessary. 

1  One  of  the  most  promising  of  these  is  the  Soldani  method  as  developed 
by  Ost  (£er.  d.  chem.  Ges.,  23,  1035,  3°°3  5  24»  l&34'>  Zeits.  anal  Cheni., 
29,  637).  The  solution  used  is  one  of  copper  carbonate  in  potassium  carbo- 
nates. I  have  had  no  experience  with  this  method. 


1 66      CHEMICAL   METHODS   OF  DETERMINING   SUGARS 

Gravimetric  Fehling  Methods. — These  are  numerous, 
but  the  same  general  principles  prevail  in  all  of  them. 
The  Fehling  solution,  or  its  modification,  is  present  in 
excess.  The  cuprous  oxide  precipitated  during  a  given 
period  of  heating,  and  under,  as  nearly  as  possible,  fixed 
conditions  of  relation  between  the  sugar,  copper  solution, 
and  dilution,  is  taken  as  a  measure  of  the  amount  of  sugar 
present.  The  reduction  is  carried  on  by  direct  boiling  or 
by  more  prolonged  heating  on  a  water  bath.  The  copper 
is  determined,  either  as  cuprous  oxide,  cupric  oxide,  or 
reduced  by  hydrogen  to  the  metal,  it  being  a  matter  of 
indifference  which,  provided  the  proper  procedure  is  fol- 
lowed. In  some  cases  the  washed  precipitate  is  dissolved 
in  nitric  acid  and  the  copper  determined  electrolytically  or 
volumetrically  by  the  usual  methods.  One  way  is  to  dis- 
solve the  washed  cuprous  oxide  in  a  standard  solution  of 
ferric  sulphate,  and  determine  the  ferrous  salt  formed  by 
standard  permanganate  solution.  Many  prefer  to  use  cop- 
per solutions  containing  more  alkali  than  the  Soxhlet  solu- 
tion contains.  Such  solutions  have  greater  sensitiveness 
to  reduction,  but  reduce  to  a  slight  extent  spontaneously, 
so  that  blank  corrections  must  be  made. 

Whatever  the  method  chosen,  the  time  and  conditions  of 
the  heating,  as  well  as  the  concentration  of  the  Fehling  liquor 
and  the  extent  of  surface  of  the  hot  solution  exposed  to  the 
air,  must  be  uniform  in  all  tests.  As  in  the  volumetric 
processes,  these  conditions  are  vital  to  accuracy. 

Usually  the  cold  sugar  solution  is  added  to  the  Fehling 
liquor  after  the  latter  has  been  heated  to  the  temperature 
at  which  the  reduction  is  carried  on.  The  length  of  time 
taken  to  add  the  sugar  solution  and  the  conditions  of 


CHEMICAL   METHODS   OF  DETERMINING   SUGARS       l6/ 

admixture  of  the  two  solutions  have  considerable  influence 
on  the  reduction,  especially  where  the  heating  is  done  on  a 
water  bath. 

As  illustrative  of  a  standard  gravimetric  method  carried 
out  by  direct  boiling,  the  following  is  that  of  Herzfeld  for 
determining  invert  sugar : 

The  solution  in  which  invert  sugar  is  to  be  determined 
is  made  up  so  that  100  cubic  centimeters  contain  20  grams 
of  sample,  after  clarification  with  basic  lead  acetate  and 
removal  of  the  soluble  lead  in  the  filtrate  by  sodium  car- 
bonate.1 The  German  way  of  doing  this  is  to  dissolve 
2 7- 5  grams  of  sample  in  125  cubic  centimeters,  the  solu- 
tion being  made  up  with  basic  lead  acetate,  as  for  polariz- 
ing, and  filtered;  100  cubic  centimeters  of  the  filtrate  are 
put  into  a  loo-uo-cubic-centimeter  double-marked  flask, 
and  10  cubic  centimeters  of  sodium  carbonate  added,  the 
solution  after  mixing  being  again  filtered. 

1.  If  the  sample  has  been  shown  to  contain  less  than 
i  per  cent  of  invert  sugar  (by  a  rough  volumetric  test, 
20  cubic  centimeters  failing  to  decolorize   12  cubic  centi- 
meters of  the  Fehling  solution  by  2  minutes'  boiling),  50 
cubic  centimeters  are  taken  for  the  exact  gravimetric  test. 

2.  If  the  sample  is  shown  to  contain  more  than  i  per 
cent  of  invert  sugar,  the  solution  containing  20  grams  of 
sample  in  100  cubic  centimeters  must  be  diluted  to  corre- 
spond to  one  made  from  a  sample  containing  i  per  cent 
of  invert  sugar.     This  dilution  is  determined  with  sufficient 
exactness  by  preparing  in  large  test  tubes  dilute  solutions 
containing  respectively  i,  2,  3,  4,  and  5  cubic  centimeters 

1  Potassium  oxalate  is  preferred  by  some  (Sawyer,/.  Am.  Chem.  Soc.y  26, 
1631). 


1 68       CHEMICAL   METHODS   OF   DETERMINING   SUGARS 

of  the  20-gram  solution,  adding  5  cubic  centimeters  of 
Fehling  solution,  and  boiling  two  minutes.  The  tube  show- 
ing a  solution  which  (after  the  copper  precipitate  has  been 
removed  by  subsidence  or  filtration)  is  still  blue  but  lightest 
in  tint  is  noted,  and  twenty  times  the  number  of  cubic  centi- 
meters of  original  solution  contained  in  this  tube  is  dis- 
solved in  100  cubic  centimeters.  Of  this  final  solution, 
50  cubic  centimeters  is  used  as  before,  for  the  exact 
gravimetric  test,  which  is  as  follows : 

Fifty  cubic  centimeters  of  the  sugar  solution  are  mixed 
with  25  cubic  centimeters  each  of  the  two  constituent  solu- 
tions of  the  Fehling  liquor,  in  a  25o-cubic-centimeter  beaker, 
and  the  whole  heated  on  a  wire  netting  on  which  is  laid  a 
sheet  of  asbestos  paper  having  a  circular  hole  cut  in  it  6.5 
centimeters  in  diameter.  The  flame  of  the  burner  is  so 
regulated  that  it  takes  3^  to  4  minutes  to  bring  the  con- 
tents of  the  beaker  to  a  boil.  Then  the  boiling  is  con- 
tinued 3  minutes  exactly,  when  the  beaker  is  immediately 
cooled  by  the  addition  of  100  cubic  centimeters  of  cold  dis- 
tilled water.  Evidently  all  the  conditions  for  a  constant 
factor  of  reduction  exist  in  this  method  except  the  inevi- 
tably variable  proportion  of  sugar  to  the  copper  solution ; 
but,  as  this  variable  is  measured  by  the  amount  of  cuprous 
oxide  precipitated,  a  table  has  been  devised  by  Herzfeld 
giving  the  equivalent  of  sugar  for  the  weight  of  copper 
obtained.  Herzfeld  has  made  his  tables  for  invert  sugar 
determination  and  determined  the  reduction  by  the  amount 
of  copper  actually  obtained  by  reduction  from  the  oxide.1 
The  precipitate  is  collected  in  a  "Soxhlet  tube,"  a  long, 
straight  funnel  tube  packed  at  the  lower  end  with  asbestos 

1  See  Appendix,  Tables  Nos.  7  and  8. 


CHEMICAL  METHODS   OF  DETERMINING  SUGARS       169 

held  in  place  with  a  platinum  sieve.  The  tube  is  placed 
on  a  suction  flask  and  the  Fehling  liquor  with  the  precipi- 
tated cuprous  oxide  poured  into  it  through  an  ordinary 
funnel  attached  by  means  of  a  stopper.  After  the  precipi- 
tate is  collected  and  quickly  washed  with 
hot  water,  it  is  attached  to  a  hydrogen 
generator  and  the  oxide  heated  to  glow- 
ing while  the  gas  is  passing.  This 
quickly  reduces  the  oxide  to  the  metallic 
state.  The  tube  is  then  placed  in  a 

desiccator  and,  after  cooling  and  coming    FIG.  29.  — SOXHLET 

.    ,  -TT-  •  '-LU     ^  i.  TUBE  WITH  FUN- 

into    equilibrium   with    the    atmosphere,        NEJ  ATTACHEDt 

is  weighed.  Special  platinum  dishes 
equipped  with  tubulated  covers  have  been  devised  in 
which  the  cuprous  oxide,  collected  on  a  filter  paper  in 
the  ordinary  way,  can  be  reduced  and  more  conveniently 
weighed.  Sometimes  the  cuprous  oxide  is  weighed  directly 
by  washing  in  a  Gooch  crucible,  and  then  adding  10  cubic 
centimeters  of  alcohol  and  afterward  10  cubic  centimeters 
of  ether,  then  drying  at  100°  C.  for  half  an  hour. 

Another  way  is  to  heat  the  cuprous  oxide,  collected  in  a 
Gooch  crucible,  to  redness  for  fifteen  or  twenty  minutes. 
This  converts  it  into  the  cupric  oxide,  which  is  more  stable 
than  the  cuprous.  Cupric  oxide  is,  however,  very  hygro- 
scopic, and  requires  special  care  in  handling,  to  avoid  error 
from  moisture.  Obviously  it  is  immaterial  whether  the  re- 
duction tables  are  figured  in  weights  of  copper  or  copper 
oxide,  as  the  values  are  convertible  by  the  appropriate 
factors. 

The  method  of  Defren,1  adapted  from  O'Sullivan,  can  be 

1 J.  Am.  Chem.  Soc,,  1896,  18,  749.     Tech.  Quart.,  1897,  IO>  I^7« 


I/O      CHEMICAL   METHODS  OF  DETERMINING   SUGARS 

taken  as  illustrating  the  conduct  of  the  test  by  heating  on 
the  water  bath.  In  this  method  15  cubic  centimeters  each 
of  the  white  and  blue  solutions  of  the  Fehling  liquor  are 
taken  in  a  loo-cubic-centimeter  Erlenmeyer  flask,  propor- 
tioned so  that  its  base  diameter  is  between  one  third  and 
one  half  of  its  height.  The  Fehling  liquor  is  diluted  with 
50  cubic  centimeters  of  water,  and  heated  by  immersion  in 
the  water  for  5  minutes,  in  order  to  come  to  the  bath  tem- 
perature. Then  25  cubic  centimeters  of  the  sugar  solution 
are  run  in  and  thoroughly  mixed,  and  the  solution  heated  for 
exactly  12  minutes  in  the  water  bath. 

The  precipitate  is  then  filtered  off  into  a  porcelain1 
Gooch  crucible,  having  an  asbestos  mat  about  one  centi- 
meter thick,  ignited,  and  weighed  as  the  cupric  oxide. 
Great  care  must  be  taken  in  the  preparation  of  the  asbes- 
tos used  in  these  filters.  It  must  be  thoroughly  boiled  in 
i.io  nitric  acid,  thoroughly  washed,  and  then  boiled  with  a 
10  per  cent  solution  of  caustic  soda  and  washed.  It  is 
sometimes  advisable  to  repeat  this  treatment  with  acid  and 
alkali.  The  crucible,  after  preparation  of  the  asbestos 
mat,  is  ignited  to  constant  weight. 

The  following  procedure  is  advisable  in  working  with 
porcelain  Gooch  crucibles,  to  prevent  their  cracking  :  The 
crucible,  after  removing  from  the  filter  flask,  is  placed 
on  a  "radiator,"  a  heavy,  hollow,  cast-iron  cone,  about 
7  centimeters  in  diameter,  in  the  open  base  of  which 
is  a  platinum  wire  triangle  for  holding  the  crucible.  When 
this  inverted  cone  is  heated  over  a  burner,  it  gives  out  a 
moderate,  even  heat,  which  will  not  crack  the  crucible, 
even  if  it  is  immediately  removed  from  the  filter  flask. 

1  Platinum  crucibles  can  be  used  to  advantage. 


CHEMICAL   METHODS   OF   DETERMINING   SUGARS       1 71 

After  a  few  minutes,  the  hot,  dry  crucible  is  transferred  to 
a  large  nickel  or  platinum  crucible,  heated  to  a  bright  red, 
where  the  ignition  is  completed. 

As  already  stated,  the  manner  of  applying  the  sugar 
solution  has  an  important  influence  on  the  result.  Defren's 
tables  were  calculated  for  a  reduction  taking  place  when 
the  solution  was  added  from  a  burette  to  the  flask  previ- 
ously removed  from  the  bath.  Slight  variations  in  this 
part  of  the  procedure,  in  the  time  taken  to  add  the  solu- 
tion, the  cooling  caused  by  the  admixture,  and  the  stirring, 
are  all  liable  to  make  variations  in  the  amount  of  total 
reduction. 

In  fact,  whatever  the  Fehling  method  employed,  inas- 
much as  very  slight  changes  in  the  manipulation,  not 
covered  by  tne  details  of  the  description  of  the  method, 
often  affect  the  reduction  factors  materially,  in  accurate 
work  the  analyst  should  cultivate  as  uniform  a  habit  of 
procedure  as  possible,  even  in  minor  details  of  manipula- 
tion, and  carefully  check  his  work  by  standard  sugar  solu- 
tions of  known  value,  until  his  determinations  give  results 
in  accord  with  the  tabulated  values  given  by  that  method, 
or  should  determine  the  values  for  his  own  work.  This 
is  imperative  in  cases  of  investigations  of  hydrolyzed  starch 
products,  for  instance,  where  slight  variations  in  the  reduc- 
ing value  are  significant ;  but  in  the  case  of  the  determina- 
tion of  invert  sugar  in  cane  or  beet  sugar  liquors,  where 
the  invert  sugar  content  is  small,  an  error  of  a  few  per 
cent  of  the  actual  value  obtained  is  often  insignificant, 
and  consequently  does  not  call  for  such  refinement. 

Blank  Fehling  tests  should  always  be  made  with  new 
Fehling  solution,  carrying  out  every  condition  of  the 


1/2       CHEMICAL   METHODS   OF  DETERMINING   SUGARS 

regular  sugar  determination,  for  although  with  the  Soxhlet 
solution  no  reduction  should  take  place,  sometimes  such 
Periling  liquors  do  show  "  spontaneous  reduction,"  espe- 
cially if  the  Rochelle  salt  is  of  inferior  quality.1  In  the 
case  of  the  investigation  of  certain  products,  where  the  re- 
duction is  small,  and  the  amount  of  impurity,  such  as  lime 
or  lead,  is  large,  this  must  be  removed  before  making  the 
test.  In  some  such  cases  it  will  be  better,  obviously,  to 
dissolve  the  cuprous  oxide  in  nitric  acid,  and  determine  it 
electrolytically.  The  intelligent  worker  will  modify  his 
method  according  to  circumstances.  The  dilution  of  his 
sugar  solution  should  be  taken  so  as  to  have  at  least  .1 
gram  of  precipitated  oxide. 

Cupric  Reducing  Power.  —  In  the  identification  of  the 
different  sugars  and  starch  products,  it  is  often  convenient 
to  calculate  the  reduction  as  a  value  of  the  pure  substance 
referred  to  the  reduction  value  of  an  equivalent  weight  of 
dextrose  taken  as  i.oo.  This  is  known  as  the  "cupric  re- 
ducing power "  of  the  substance,  and  symbolized  by  the 
Greek  letter  /c.  For  instance,  the  cupric  reducing  power 
of  maltose  is  .62,  that  of  invert  sugar  [95,  etc.,  which  means 
that  maltose  reduces  .62  as  much  copper  solution  as  the 
same  weight  of  dextrose  under  the  same  conditions  of  test ; 
invert  sugar,  .95  as  much. 

Under  different  conditions  of  reduction  prevailing  in 
different  methods,  the  cupric  reducing  powers  of  different 
sugars  do  not  give  the  same  constant  value. 

1  Blank  tests  also  show  whether  all  soluble  matter  has  been  removed  from 
the  asbestos  by  the  chemical  treatment  described.  The  crucible  should  show 
no  change  in  weight. 


STARCH    AND   STARCH    PRODUCTS 

Chemistry  of  Starch.  —  Starch  is  vital  to  higher  plant 
life,  and  while  widely  distributed  in  vegetable  tissue,  espe- 
cially makes  up  a  large  part  of  the  substance  of  many 
grains  and  tubers.  As  found  in  nature,  it  is  in  the  form  of 
minute  granules,  of  a  density  of  1.6,  the  shapes  of  which 
vary  much  in  starches  from  different  plants,  but  are  so 
characteristic  that  investigation  with  the  microscope  will, 
in  most  cases,  easily  determine  their  botanic  origin.  While 
authorities  differ  as  to  the  exact  structure  of  the  starch 
granule,  from  the  standpoint  of  the  chemist  it  may  be  con- 
sidered as  composed  of  a  mass  of  carbohydrate  paste, 
inclosed  in  denser  tissue  of  apparently  the  same  general 
chemical  composition,  known  as  "starch  cellulose." 

The  unbroken  starch  granule  is  insoluble  in  cold  water, 
but  if  a  mixture  of  starch  and  water  is  heated  to  about  70°, 
the  exact  point  differing  with  different  starches,  the  starch 
suddenly  swells  to  a  pasty  jelly.  The  microscope  shows 
that  this  is  the  result  of  the  expanding  of  the  interior  con- 
tents by  absorption  of  water  till  the  enveloping  tissue  of 
starch  cellulose  has  been  ruptured,  the  greatly  swollen 
jelly  contents  escaping. 

If  the  cell  structure  is  ruptured  mechanically  by  grind- 
ing starch  with  sharp  quartz  sand,  or  the  "  cellulose " 
removed  chemically  by  dilute  solutions  of  alkalies,  zinc 


1/4  STARCH   AND   STARCH   PRODUCTS 

chloride,  or  other  solvents,  the  same  thing  occurs.  At  the 
same  proportions  of  starch  arid  water,  the  consistency  of 
pastes  made  from  starches  of  different  origin  differs  much, 
and,  in  consequence,  starches  have  been  placed  in  two 
classes,  —  "thick  boiling"  and  "thin  boiling."  It  is  now 
known  that  the  conditions  of  the  process  by  which  the 
starch  has  been  extracted  from  the  plant  have  much  to  do 
with  this  pasting  property. 

Chemically  classified,  it  has  been  shown  by  Brown  and 
Millar  that  starch  paste  is  a  highly  condensed  hexose  car- 
bohydrate of  the  formula,  100  C6H10O5,  which  can  be  con- 
sidered as  an  aggregation  of  100  anhydride  groups  derived 
from  dextrose  by  the  removal  of  as  many  equivalents  of 
water.  As  would  be  expected,  such  a  complicated  body 
is  easily  resolved  by  hydrolytic  agents  into  simpler  com- 
binations, finally  becoming  dextrose,  a  result  which  can 
practically  be  attained  by  prolonged  acid  hydrolysis. 

If  the  hydrolysis  with  acid  is  followed  from  the  be- 
ginning, there  is  found  to  occur  a  gradual  disintegra- 
tion of  the  starch  into  products  which  chemically  can 
be  considered  as  molecular  aggregations  of  three  well- 
defined  compounds,  —  maltose  (C12H22On),  a  dextrin 
(C6H12O6(C6H10O5)39),  and  dextrose  (C6H12O6). 

If  an  ensym  is  used  as  the  hydrolytic  agent,  such  as 
diastase,  which  is  the  active  principle  of  malt,  the  hydroly- 
sis under  ordinary  conditions  does  not  go  on  till  dextrose 
is  the  final  product,  but  the  compounds  formed  are  aggre- 
gates of  maltose  and  dextrin  only.  The  hydrolysis  under 
different  temperature  conditions  of  the  diastase  action 
has  been  found  to  follow  well-defined  reactions.  The  one 
occurring  at  45°  C.,  and  most  favorable  for  the  production 


STARCH   AND   STARCH   PRODUCTS  1 7$ 

of  the  greatest  amount  of  maltose,  can  be  expressed  by  the 
following  reaction : 

100  C12H20010  +  8 1  H20  =  80  C12H22On 

+  (C6H10O5)39C6H12O6, 

action  ceasing  when  these  compounds  have  been  formed 
in  the  proportions  given  by  the  equation,  and  the  solution 
coming  into  chemical  equilibrium. 

In  acid  hydrolysis  there  is  a  progressive  decrease  in  the 
dextrin  constituent  as  the  action  continues,  and  a  similar 
increase  in  the  amount  of  the  dextrose  which  is  formed  in 
this  hydrolysis.  The  maltose  at  first  increases  rapidly,  but, 
after  reaching  a  maximum  of  about  45  per  cent  of  the  total 
carbohydrate,  diminishes  as  rapidly,  till,  at  the  completion 
of  hydrolysis,  it  is  entirely  converted  into  dextrose.  At  no 
point  in  the  hydrolysis,  except  at  the  very  beginning  and 
end,  are  any  of  these  constituent  carbohydrates  entirely 
absent.  The  gradual  disintegration  of  the  starch  molecule 
and  the  different  stages  of  the  hydrolysis  of  the  products 
of  this  disintegration  all  go  on  at  the  same  time,  so  that 
the  final  products  of  hydrolysis  are  always  present  in  very 
small  quantity  even  at  the  initial  stages  of  the  hydrolysis. 

The  progression  of  the  hydrolysis  manifests  itself  in  the 
following  characteristics  :  The  starch  paste  gradually  loses 
its  colloidal  nature  and  passes  over  to  a  thin  sirup,  its 
viscosity  continually  decreasing.  The  dissolved  carbohy- 
drate increases  in  weight,  but  the  density,  proportionally, 
continually  decreases,  that  is  to  say,  the  density  effect 
of  a  given  weight  of  carbohydrate  in  a  given  volume  of 
solution  continually  decreases.  The  specific  rotation  of 
the  carbohydrate,  taken  as  a  whole,  likewise  decreases, 


1/6  STARCH  AND   STARCH   PRODUCTS 

while  its  cupric-reducing  power  increases,  these  values 
progressively  approaching  those  for  dextrose. 

The  iodine  tests  are  also  characteristic ;  a  few  drops  of 
iodine  solution  giving,  with  the  hydrolyzed  solutions,  at 
ordinary  temperature,  colors  which  change  progressively 
as  the  hydrolysis  proceeds,  from  the  deep  sapphire  blue  of 
the  unchanged  starch,  first  to  violet  and  reddish  purple,  then 
to  a  rose  madder,  and  then  to  a  reddish  brown,  growing 
lighter  as  the  conversion  proceeds,  till  at  a  later  stage,  but 
before  hydrolysis  is  complete,  the  iodine  gives  no  color 
reaction. 

These  colors  are  so  characteristic  that  an  expert  can 
follow  the  progress  of  the  hydrolysis  with  considerable 
precision.  In  commercial  hydrolytic  processes,  as  the 
manufacture  of  "  commercial  glucose,"  they  are  depended 
on  to  define  the  requisite  point  of  "  conversion." 

By  precipitation  with  alcohol,  numerous  well-defined 
compounds,  known  as  "dextrins,"  can  be  separated  from 
hydrolyzed  starch  products,  which  give  colorations  with 
iodine  corresponding  to  the  degree  of  hydrolysis  of  the 
starch  solution  from  which  they  were  obtained.  These 
products  behave,  however,  chemically  and  optically,  as  if 
they  were  mixtures  of  maltose,  dextrose,  and  the  primary 
constituent  dextrin  already  alluded  to,  so  they  need  not  be 
considered  here.  Other  reactions  of  starch  will  be  referred 
to  only  when  necessary  for  explanation  of  the  subject  at 
hand. 

Commercial  Starch. — Although  starch  is  so  widely  dis- 
tributed in  Vegetable  tissue,  constituting  a  large  proportion 
of  our  food  products,  comparatively  few  plants  are  utilized 
in  making  the  commercial  product.  Among  these,  by  far 


STARCH   AND   STARCH   PRODUCTS  177 

the  most  important  in  this  country  is  Indian  corn  (maize). 
In  Europe,  starch  is  made  almost  exclusively  from  potatoes ; 
some  potato  starch  is  made  in  this  country  also.  Wheat 
starch  is  likewise  of  commercial  importance,  the  starch 
being  manufactured  from  flour.  Tapioca  and  rice  starches 
are  made  in  the  far  East,  and  brought  to  this  country,  the 
former  being  a  recent  product  of  Florida  from  the  cassava 
root. 

The  general  methods  of  starch  manufacture  naturally 
fall  into  two  classes:  (i)  those  in  which  the  albuminous 
by-products  (gluten)  are  saved  and  utilized ;  (2)  processes 
where  the  gluten  is  decomposed  by  fermentation  or  chemi- 
cal methods. 

Originally,  the  gluten  was  removed  entirely  by  fermen- 
tation and  lost,  but  by  modern  methods  most  of  this  is 
now  saved  and  utilized  in  various  ways.  The  ferment 
acids  arising  from  the  destruction  of  the  gluten  by  the 
older  processes  always  produced  an  incipient  hydrolysis 
which  made  the  starch  to  a  greater  or  less  degree  "thin 
boiling." 

The  general  principles  of  process  of  making  commercial 
starches  are  as  follows  :  ( i )  Breaking  down  the  plant  tissue 
in  such  a  way  that  the  starch  grains  are  set  free  but  not 
ruptured.  (2)  Separation  from  the  gluten,  usually  by  dilut- 
ing the  mixture  of  starch  and  gluten  with  a  large  amount  of 
water,  and  then  settling  out  the  heavy  starch  by  subsidence 
in  tanks  or  by  flowing  the  diluted  mixture  down  long,  very 
slightly  inclined  canals  ("runs")  in  which  the  starch  is 
deposited.  (3)  Washing  the  starch  by  agitating  with  water 
in  tanks.  (4)  Draining  off  the  starch  from  the  starch 
"  milk  "  in  cloth-bottom edNf  draining  boxes  "  or  in  filter 


178  STARCH   AND   STARCH   PRODUCTS 

presses  of  special  design.  (5)  Drying  the  starch  in  hot 
rooms  ("kilns"). 

Grains  have  to  be  steeped  in  warm  water  for  several 
days  before  they  can  be  ground.  In  the  case  of  wheat 
starch,  the  gluten  of  which  is  thick  and  rubbery,  balls 
of  dough  prepared  from  flour  are  worked  in  a  special 
kneading  machine,  the  starch  being  washed  out  during 
the  kneading  by  jets  of  water. 

As  already  stated,  starches  derived  from  different  plants 
vary  considerably  in  the  thickness  ("body")  of  the  pastes 
they  make  when  mixed  with  hot  water,  some  being  quite 
liquid,  others,  at  the  same  concentration,  being  too  dense 
to  flow.  It  has  been  found  that  this  quality  of  the  starch 
depends  largely  on  the  amount  of  hydrolytic  change  to 
which  the  starch  has  been  subjected  in  the  necessary  detail 
of  process.  Consequently,  manufacturers  have  learned  to 
control  this  pasting  property  to  a  considerable  extent,  so 
that  products  can  be  made  to  suit  the  special  requirements 
of  the  customer. 

The  manufacture  of  corn  starch  is  by  far  the  most  im- 
portant branch  of  the  industry,  and  in  no  other  has  the 
utilization  of  by-products  and  the  development  of  manu- 
factures derived  from  starch  been  carried  so  far. 

As  corn  starch  is  made  in  conjunction  with  glucose 
and  grape  sugar,  special  reference  will  be  made  to  this 
later. 

Methods  of  determining  Starch.  —  Numerous  methods 
have  been  proposed  for  the  determination  of  starch,  espe- 
cially in  grains  and  foods  prepared  from  grains.  Most  of 
them  depend  on  the  following  principles,  it  being  advisable 
and  in  some  cases  necessary  to  dry  the  sample  and  remove 


STARCH   AND    STARCH   PRODUCTS  179 

the  fats,  and  of  course  essential  in  every  case  that  the  sam- 
ple be  ground  to  the  greatest  possible  fineness,  and  that  all 
other  carbohydrates  which  are  soluble  in  water  or  alcohol, 
such  as  sugars,  gums,  and  dextrins,  be  previously  extracted  : 
(i)  Dissolving  out  the  starch  by  hydrolyzing  with  malt 
extract,  and  determining  the  starch  by  difference.  (2)  Com- 
pletely hydrolyzing  the  starch  with  hydrochloric  acid,  and 
determining  the  dextrose  formed  by  the  Fehling  method. 
(3)  Dissolving  and  filtering  off  the  starch  as  in  (i),  then 
completing  the  hydrolysis  with  acid  and  determining  the 
dextrose.  (4)  Same  as  (3),  except  that  starch  is  dissolved 
by  heating  with  water  under  steam  pressure  of  about 
three  atmospheres,  by  means  of  an  autoclave.  (5)  Partially 
hydrolyzing  with  salicylic  or  nitric  acid,  and  polarizing  the 
solution.  (6)  Determining  the  amount  of  standard  barium 
hydrate,  which  will  combine  with  the  pasted  starch.  None 
of  these  methods  are  very  satisfactory,  although  most  of 
them  are  accurate  with/z/;r  starch. 

The  solution  method,  in  which  the  starch  is  determined 
by  difference,  assumes  that  starch  (from  which  the  water- 
soluble  carbohydrates  have  been  removed)  alone  is  dis- 
solved out  by  malt  extract,  but  it  is  known  that  some  of 
the  proteid  matter  is  also  dissolved. 

With  the  acid-hydrolysis  method,  in  the  case  of  grains 
particularly,  other  carbohydrates  which  are  present,  espe- 
cially "pentosans," — carbohydrates  containing  five  equiva- 
lents of  carbon,  of  the  general  formula  (C5H8O4)W,  analogues 
of  starch, — are  hydrolyzed  into  pentose  sugars,  which  also 
reduce  Fehling  solution,  and  so  introduce  error. 

The  polariscope  methods  are  unsatisfactory,  owing  to  the 
difficulty  in  getting  clear  solutions  and  the  large  amount 


I  So  STARCH   AND   STARCH   PRODUCTS 

of  substance  required.  The  barium  method  is  of  doubtful 
reliability,  except  with  very  pure  starches.  The  methods 
following  the  principles  given  in  (3),  in  which  the  starch  is 
partially  converted  by  malt  extract,  and  separated  from  the 
other  substance  previous  to  completing  the  conversion  to 
dextrose,  are  considered  the  most  reliable,  as  experimental 
evidence  tends  to  show  that  pentosans  are  unaffected  by 
diastase,  which  is  the  active  enzym  of  malt. 

When  pentosans  are  absent,  the  method  of  Sachsse  by 
simple  acid  hydrolysis  is  the  standard,  and  is  as  follows : 
An  amount  of  dry  substance  containing  2.5-3  grams  of 
starch  is  heated  on  a  boiling-water  bath  with  20  cubic 
centimeters  of  hydrochloric  acid,  of  a  density  of  1.125 
(the  ordinary  "  dilute  "  reagent),  and  200  cubic  centimeters 
of  water,  in  a  flask  with  an  air  condenser  (a  long,  straight 
glass  tube  passed  through  the  stopper)  for  three  hours ; 
or  the  flask  is  fitted  with  a  return  Liebig  condenser,  or 
one  of  similar  type,  and  kept  boiling  by  a  direct  flame  for 
one  hour  and  a  half.  The  contents  of  the  flask,  after 
cooling,  are  then  neutralized  with  sodium  hydrate,  care 
being  taken  not  to  get  it  alkaline  (very  faint  acidity  does 
no  harm),  made  up  to  500  cubic  centimeters,  and  the  dex- 
trose determined  by  Fehling  solution.  By  the  simple 
formula,  C12H.20O10  +  2  H2O  =  2  C6H12O6,  the  equivalent 
of  starch  is  .9  the  amount  of  dextrose.  Experiment  has 
shown  that  there  is  always  a  certain  amount  of  decomposi- 
tion in  the  complete  hydrolysis  of  starch  to  dextrose,  so 
that  the  factor  .92,  according  to  Wiley  and  Krug,  gives 
more  accurate  results. 

The  diastase  method,  according  to  Wiley,1  being  practi- 

1  Agric.  Chem.  Anal.,  3,  198. 


STARCH    AND    STARCH    PRODUCTS  l8l 

cally  the  Halle  (Agricultural  Station) method,  is  as  follows: 
About  3  grams  of  the  finely  pulverized  material  is  ex- 
tracted, first  with  ether,  and  then  with  10  per  cent  alcohol, 
and  boiled  with  100  cubic  centimeters  of  water  for  30 
minutes  with  constant  stirring,  to  set  free  the  starch  paste. 
The  water  lost  by  evaporation  is  replaced,  and  the  mix- 
ture placed  in  a  water  bath  at  55-60°  C.  When  the  liquid 
las  cooled  to  the  water-bath  temperature,  10  cubic  centi- 
meters of  fresh  malt  extract  are  added,  and  the  whole  is 
digested  for  an  hour  with  occasional  stirring.  The  mix- 
ture is  then  digested  for  15  minutes  with  another  10  cubic 
centimeters  of  malt  extract.  This  treatment  is  again 
repeated.  The  mixture  is  then  filtered,  made  up  to  250 
cubic  centimeters,  and  200  cubic  centimeters  is  hydrolyzed 
according  to  the  Sachsse  method,  two  hours  being  sufficient 
for  the  acid  hydrolysis  on  the  water  bath.  The  malt  extract 
is  made  by  soaking  100  grams  of  fresh  malt  in  100  cubic 
centimeters  of  cold  water  for  two  or  three  hours,  and  filter- 
ing ;  or,  as  recommended  by  Wiley  for  a  more  permanent 
extract,  1000  grams  of  finely  ground  "green"  (not  kiln- 
dried)  malt  is  mixed  with  a  liter  of  glycerine  and  allowed 
to  stand  for  eight  days  with  frequent  shaking.  It  is  then 
filtered  under  pressure,  and  again  by  ordinary  filtration. 
This  extract  is  said  to  keep  well. 

As  malt  extracts  always  contain  some  reducing  sugars, 
blank  Fehling  tests  must  be  made  to  determine  the  neces- 
sary correction  to  be  applied.  Hibbard's  modification  of 
the  diastase  method  for  rapid  work  is  as  follows :  Previous 
extraction  with  ether  is  omitted.  Enough  of  the  mixture 
to  contain  at  least  .5  gram  of  starch  is  placed  in  a  flask 
with  50  cubic  centimeters  of  water  and  about  2  cubic 


1 82  STARCH   AND   STARCH    PRODUCTS 

centimeters  of  malt  extract,  and  heated  to  boiling  with 
frequent  shaking  to  prevent  pasting.  The  mixture  is 
boiled  one  minute,  cooled  to  60°  C,  and  2  or  3  cubic, 
centimeters  of  malt  extract  again  added.  It  is  then 
heated  gradually  to  boiling,  taking  15  minutes,  cooled, 
and  tested  with  iodine  for  any  unchanged  starch.  If 
starch  is  shown,  the  operation  must  be  repeated.  The 
rest  of  the  procedure  is  as  in  the  method  previously 
described. 

In  any  method  where  diastase  is  used  as  a  solvent,  the 
residue  from  the  filtrate  of  the  malt-converted  liquor  should 
be  examined  for  unconverted  starch. 

Wiley  recommends  the  use  of  pepsin  in  conjunction  with 
malt  extract  as  a  solvent  of  the  proteid  matter  which  in- 
closes the  starch  granules  and  interferes  with  the  solution 
of  the  latter. 

Optical  and  Reducing  Properties  of  Hydrolyzed  Starch 
Products.  —  It  is  impossible  to  polarize  pure  starch,  as  it 
forms  a  colloidal  solution  which  is  practically  opaque, 
except  in  very  dilute  solutions ;  the  liquid  solutions  of  some 
starches,  so  called,  being  really  of  starch  which  has  under- 
gone an  incipient  hydrolysis  in  the  process  of  extraction 
from  the  plant  tissues,  or  in  the  treatment  for  polarizing. 
Pure  starch  can  be  shown  theoretically  to  have  a  specific 
rotation  of  about  202°.  It  gives  no  reduction  with  Fehling 
solution.  If  starch  is  hydrolyzed  with  acids,  there  is  a 
regular  decrease  in  the  rotation,  and  a  reducing  power  is 
developed  which  shows  a  corresponding  increase  as  the 
rotatory  power  decreases,  till  the  specific  rotation  becomes 
practically  constant  at  52.7  and  the  cupric-reducing  power 
becomes  i.oo.  If  the  heating  is  prolonged  and  the  hydrolyz- 


STARCH  AND   STARCH   PRODUCTS  183 

ing  acid  of  considerable  strength,  these  exact  figures  are 
not  obtained,  owing  to  a  small  amount  of  decomposition 
products  which  is  formed. 

Investigations  made  in  the  laboratory  of  the  Massa- 
chusetts Institute  of  Technology1  have  shown  that  a  defi- 
nite relation  exists  between  the  specific  rotation  and  the 
cupric-reducing  power  of  acid-hydrolyzed  starch  products 
at  every  stage  of  conversion;  in  other  words,  strong  ex- 
perimental evidence  tends  to  prove  that  the  cupric-reduc- 
ing power  of  any  normally  acid-hydrolyzed  starch  product 
can  be  predicted,  if  its  specific  rotation  is  known.  The 
relation  of  the  cupric-reducing  power  plotted  from  actual 
experimental  results  shows  a  curve  which  cuts  the  o  and 
i.oo  points,  expressing  the  cupric-reducing  values,  very 
nearly  at  rotations  of  202°  and  52.7°  respectively.2  This 
means  that  all  acid-hydrolyzed  products  of  the  same  spe- 
cific rotation  have  the  same  composition,  and  consequently, 
the  determination  of  specific  rotation  is  a  rapid  means  of 
identifying  such  (pure)  products.  A  similar  law  of  rela- 
tion has  been  proved  by  Brown  and  Morris  to  exist  in  all 
diastase-hydrolyzed  starch  products.  In  this  latter  case, 
the  law  of  relation  is  represented  in  plot  by  a  straight  line, 
the  cupric-reducing  values  of  o  and  .62  being  at  points  of 
specific  rotation  of  203°  and  138°  respectively;  the  value 
.62  is  the  cupric-reducing  power  and  138°  the  specific  rota- 
tion of  pure  maltose,  which  is  the  final  product  present  in 
malt  (diastase)  converted  starch. 

1J.  Am.  Chem.  Soc.,  18,  869;  ibid.,  25,  1003.  Wiley  pointed  out  a  simi- 
lar relation  in  the  case  of  commercial  glucose  as  early  as  1882  (Proc.  A.  A. 
A.  S.,  30,  65). 

2  See  diagram  on  page  198. 


1 84  STARCH   AND    STARCH    PRODUCTS 

Methods  of  Analysis  of  Acid-hydrolyzed  Starch  Products. 
—  As  already  stated,  acid-hydrolyzed  starch  products  can 
be  considered  to  be  composed  of  three  primary  constitu- 
ents, dextrose,  maltose,  and  dextrin.  These  constituent 
bodies  cannot  be  isolated  from  each  other  except  by  a 
tedious  and  complicated  procedure  impracticable  for  most 
commercial  analysis.  In  consequence,  an  ingenious  indi- 
rect method  has  been  worked  out  by  which  the  proportions 
of  the  primary  constituents  are  calculated  from  the  results 
of  three  determinations,  —  the  total  solids,  the  specific  rota- 
tion, and  the  cupric-reduciug  power.  The  acid-hydrolyzed 
product  being  pure,  evidently,  if  the  per  cents  of  dextrose, 
dextrin,  and  maltose  are  expressed  (as  decimals)  by  D,  A, 
and  ;;/  respectively,  the  composition  of  the  carbohydrate  sub- 
stance will  be  expressed  by  the  following  equation : 

D  +  m  +  A  =  i.  (i) 

As  the  specific  rotatory  power  of  dextrose  is  52.7,  that 
of  maltose  138,  and  dextrin  203,  the  specific  rotatory 
power  of  the  hydrolyzed  product  is  given  by  the  following  : 

52.7  D  +  138  m  +  203  A  =  a/,.  (2) 

Two  of  the  constituents,  dextrose  and  maltose,  give  re- 
duction by  the  Fehling  method,  maltose  having  .62  the 
reducing  power  of  dextrose.  This  stable  dextrin  is 
usually  considered  to  be  non-reducing  (although  the  re- 
searches of  Brown  and  Millar 1  have  recently  shown  that 
the  corresponding  and  probably  identical  dextrin  of  dias- 
tase conversion  has  a  cupric-reducing  power  of  about  .03). 

1y.  Chem.  Soc.,  75,  322. 


STARCH   AND   STARCH    PRODUCTS  185 

The  following  equation  would  then  express  the  cupric- 
reducing  power  of  the  acid  hydrolyzed  product : 

K  =  D  +  .62  m.  (3) 

From  the  three  independent  equations,  the  values  of  /?, 
m,  and  A  can  be  determined. 

Total  Solids.  —  In  order  to  determine  the  optical  and 
reducing  constants,  it  is  necessary  to  know  the  exact 
amount  of  pure  carbohydrate  in  the  solution  analyzed. 
As  the  amount  of  organic  matter,  other  than  carbohydrate, 
in  starch  products  is,  as  a  rule,  negligible,  the  total  solids, 
-less  the  mineral  matter,  which  can  be  determined  as  ash, 
represent  the  total  products  of  hydrolysis. 

As  already  stated,  it  is  practically  impossible  to  deter- 
mine the  total  solids  of  a  saccharine  solution  with  any 
accuracy  by  the  ordinary  methods  of  drying,  and  in  fact 
no  reliable  method  at  all  was  known  till  comparatively 
recently.  On  this  account,  it  had  become  customary  for 
glucose  and  brewery  chemists  to  use  the  density  of  the 
solution  as  a  measure  of  the  amount  of  dissolved  carbo- 
hydrate, it  being  assumed  that  the  density  influence  of  the 
carbohydrate  constituents  is  identical  with  that  of  cane 
sugar;  that  is,  if  the  solution  has  an  approximate  concen- 
tration of  10  per  cent,  every  gram  of  carbohydrate  present 
in  100  cubic  centimeters  of  solution  at  15.5°  C.  increases  the 
density  (referred  to  water  at  1 5.5°  C.)  by  .00386.  The  solu- 
tions must  approximate  10  per  cent,  as  both  the  density  fac- 
tor and  specific  rotatory  power  vary  with  the  concentration. 

By  this  method,  first  introduced  by  O'Sullivan  in  I8/6,1 
the  amount  of  total  solids  of  a  solution  of  pure  carbo- 

1  O'Sullivan's  original  factor  was  .00385,  it  being  subsequently  changed  by 
Brown  and  Heron  to  .00386. 


1 86  STARCH   AND   STARCH   PRODUCTS 

hydrates  resulting  from   starch    hydrolysis  was  assumed 

to  be  given  by  the  formula,  w  =     ~~  l'O(:—,  this  equation 

.00380 

being  correct  for  10  per  cent  solutions  of  cane  sugar,  within 
about  .1  per  cent.  If  mineral  matter  be  present,  as  it 
usually  is  in  small  amount,  .008  for  every  gram  of  ash 
obtained  from  100  cubic  centimeters  of  the  solution  must 
first  be  deducted  from  the  density  actually  obtained  in  order 
to  determine  the  density  due  to  the  carbohydrate  alone. 
The  density  is  determined  most  accurately  by  the  "  pyk- 
nometer,"  although  the  "  Westphal  balance"  is  sufficiently 
accurate  in  careful  hands  for  most  work.  In  commercial 
analyses  in  general  factory  control,  the  Brix  spindle  can  be 
used,  this  giving  the  per  cent  of  total  solids  directly  without 
calculation,  except  for  the  mineral  matter  present,  which 
must  be  corrected  for. 

Determination  of  Density.1  The  Westphal  Balance.— 
The  essential  parts  of  this  apparatus  are  a  glass  hydrometer 
sinker  counterpoised  on  a  delicate  balance.  The  weights 
are  in  the  form  of  riders,  which  are  designed  to  be  hung 
on  the  balance  arm  which  carries  the  sinker,  the  other  arm 
serving  to  carry  the  fixed  counterpoise  weight  (K)  which 
balances  the  sinker  in  air.  The  weighing  arm  (H)  is  gradu- 
ated into  tenths  by  deep  notches  cut  in  the  beam,  each  notch 
being  numbered  according  to  the  number  of  tenths  of  the 
distance  from  the  center  to  the  end  knife-edge  it  represents. 
The  largest  rider  weight  hung  on  the  stirrup  hook  (E)  just 
balances  the  buoyancy  of  the  sinker  when  it  is  immersed 

1  The  term  "  density "  is  used  throughout  this  book  as  synonymous  with 
"  specific  gravity."  Both  values  are,  of  course,  identical  for  practical  labora- 
tory work. 


1 88  STARCH    AND   STARCH    PRODUCTS 

in  water  at  the  standard  temperature,  usually  15.5°  C.  The 
glass  sinkers  are  commonly  made  so  that  they  displace 
exactly  5  grams  of  water  at  the  standard  temperature,  and 
with  the  platinum  suspending  wire  and  hook  weigh  exactly 
10  grams,  so  that  they  are  interchangeable.  In  most  types 
a  thermometer  is  inclosed  in  the  sinker. 

The  other  rider  weights  are  decimals  of  the  largest, 
weighing  respectively  .5,  .05,  .005  grams,  each  rider 
being  readily  distinguished  by  its  size.  As  a  large  rider  (A), 
placed  on  the  stirrup  hook,  just  balances  the  buoyancy  of 
the  water  displaced  by  the  sinker  at  standard  temperature, 
showing  a  density  of  i.oooo,  evidently  the  sinker  immersed 
in  a  liquid  of  a  density  of  i.iooo  will  be  balanced  by  the 
addition  of  the  .5-gram  rider  oh  the  stirrup  hook,  an  in- 
crease of  .01  in  the  density  requiring  the  .O5-gram  rider 
to  be  placed  on  the  stirrup  hook,  —  and  so  on.  So,  too,  it 
will  be  clear  that  the  5-gram  rider  in  any  notch  on  the  beam 
represented  by  the  number  of  its  graduation, ;/,  will  balance 
the  buoyancy  of  the  liquid  caused  by  any  increase  in  den- 
sity corresponding  to  .1  ;/,  the  .5-gram  rider  (B)  any  incre- 
ment in  density  corresponding  to  .01  «,  etc.  For  instance, 
if  the  balance  is  in  equilibrium  when  the  sinker  is  immersed 
in  a  liquid  at  15.5°,  and  one  5-gram  rider  is  on  the  stirrup 
hook,  another  5-gram  rider  in  the  beam  notch  marked  i, 
the  .5-gram  rider  in  notch  marked  4,  the  .O5-gram  rider  (C) 
in  notch  marked  6,  and  the  .oo5-rider  (not  shown  in  cut)  in 
notch  numbered  8,  the  density  of  the  solution  is  1.1468. 
Thus,  by  noting  the  numbered  position  of  each  rider  on  the 
beam,  and  its  size,  tJie  density  can  be  read  off  directly  with- 
out calculation.  (See  other  illustrations  of  readings  in 
Figure  30.) 


STARCH   AND   STARCH   PRODUCTS  189 

In  using  the  Westphal  balance,  the  sinker  (5)  is  first  care- 
fully balanced  in  air,  by  adjusting  the  leveling  screw  (G)  in 
the  balance  foot.  The  sinker  is  then  immersed  in  the  liquid, 
care  being  taken  to  remove  any  adhering  air  bubbles - 
most  conveniently  by  means  of  a  fine  wire.  Care  should 
be  taken  also  to  have  always  the  same  length  of  support- 
ing wire  of  the  sinker  immersed  in  the  liquid;  just  how 
much  being  determined  once  for  all  by  calibrating  the 
balance  with  pure  water  at  the  standard  temperature,  and 
marking  a  line  on  the  adjustable  supporting  post  (L)  of  the 
balance,  and  another  on  the  glass  cylinder  used  to  contain 
the  liquid.  This  latter  mark  will  show  the  height  that  the 
cylinder  must  always  be  filled  to  give  the  proper  im- 
mersion of  the  wire  when  the  height  of  the  balance  is 
adjusted  to  the  mark  on  the  post  by  the  set  screw  P. 
The  Sartorius  type  of  Westphal  is  so  marked  by  the 
maker. 

A  well-made  Westphal  balance  should  be  precise  to 
.0005  gram,  and  consequently  should  have  the  same  care 
as  any  other  analytical  balance. 

Determination  of  Density  by  the  Pyknometer.  —  This  is 
the  most  precise  method.  There  are  many  forms  of  pyk- 
nometers,  but  most  of  the  ordinary  types  used  for  determi- 
nations of  densities  by  weighing  20  cubic  centimeters  or 
more  of  solution  are  practically  identical  in  principle,  — 
light  flasks  which  are  devised  so  that  they  can  be  accurately 
filled  to  a  fixed  volume  within  an  error  represented  by  the 
difference  in  weight  of  about  .001  gram,  the  point  of  level 
of  the  liquid  filling  the  pyknometer  being  read  off  in  a 
capillary  tube.  Usually  there  is  a  thermometer  attached, 
and  a  tightly  fitting  cap  for  the  capillary  tube,  so  as  to 


190  STARCH  AND  STARCH   PRODUCTS 

retain  any  water  expanding  out  of  the  flask  during 
weighing. 

The  method  of  using  the  pyknometer  is  as  follows: 
The  weight  of  the  carefully  cleaned  and  dried  apparatus 
is  taken,  or  it  is  balanced  with  a  tare  weight.  The  pyk- 
nometer is  then  filled  with  freshly  boiled  water  at  a  tempera- 
ture somewhat  lower  than  the  standard,  and  then  allowed 
to  warm  up  till  the  thermometer  shows  that  the  standard 
temperature  is  reached,  or,  for  greater  accuracy,  brought 
to  the  standard  temperature  by  immersion  in  a  cold-water 
bath.  The  liquid  which  has  oozed  from  the  capillary  is 
then  carefully  wiped  off,  and  the  opening  closed  with  the 
glass  cap  (or  in  some  forms  of  pyknometer,  the  level  of  the 
liquid  in  the  capillary  is  merely  brought  to  a  mark).  The 
pyknometer  is  again  weighed.  In  this  manner  the  weight 
of  water  the  pyknometer  contains  at  standard  temperature 
is  obtained  once  for  all,  this  expressing  the  volume  in  Mohr 
cubic  centimeters. 

The  weight  of  any  solution  contained  by  the  pyknometer 
at  standard  temperature,  obtained  in  the  same  way,  divided 
by  the  volume,  gives  the  density  relative  to  its  volume  in 
Mohr  cubic  centimeters.  Absolute  densities  (referred  to  vol- 
umes in  true  cubic  centimeters  at  20°  C.)  can  be  calculated 

by  the  formula,  d~^~= -°,  where  wf  is  the  weight  of  solu- 
tion and  w  the  weight  of  water,  both  taken  at  20°,  D^ 
being  the  density  of  water  at  20°. 

As  the  air  buoyancy  has  practically  the  same  influence 
on  both  weights,  reduction  to  vacuo  is  unnecessary  for  or- 
dinary-sized pyknometers. 

A  very  convenient  pyknometer,  used  by  the  author  in 


STARCH  AND   STARCH   PRODUCTS 


\ 


A 

V 

f 

; 

the  laboratory  of  Professor  J.  M.  Crafts,  is  shown  in  the 
following  sketch : 

The  pyknometer  is  designed  to  be  used  with  a  constant 
temperature  bath,  the  reference  point  by  which  the  volume 
is  measured  being  marked  on 
the  funnel  stem.  The  method 
of  using  is  by  filling  the  flask 
through  the  funnel  tube,  and 
after  bringing  the  contents  to 
the  standard  temperature  by 
means  of  the  water  bath,  gently 
inclining  the  apparatus  so  that 
the  liquid  dropping  out  of  the 
capillary  sinks  to  the  mark  A 
on  the  funnel  stem. 

The  pyknometer  can  then 
be  placed  upright  on  the  bal- 
ance pan  and  weighed  at  con- 
venience, as  there  is  ample 
room  for  the  liquid  to  expand 
from  any  change  in  ordinary 
laboratory  temperature,  without  spilling  out  of  the  pyk- 
nometer. 

As  stated,  it  is  customary  in  commercial  work  to  deter- 
mine the  constituents  of  both  malt  and  acid  converted 
starch  products,  such  as  beer  worts,  commercial  "glucose," 
and  grape  sugar,  by  determining  the  carbohydrates  from 
the  density  by  means  of  the  factor  .00386.  Obviously,  the 
true  specific  rotatory  and  cupric-reducing  constants  are  in 
F 


FIG.  31.  —  DIAGRAM  OF  CON- 
VENIENT PYKNOMETER. 


the  ratio  of 


.00386 


to  the  values  obtained  by  this  method^ 


1  92  STARCH   AND   STARCH    PRODUCTS 

where  F  represents  the  true  density  factor  of  the  product 
examined.  If  the  primary  constituents  are  calculated  by 
the  equation  already  given,  the  percentages  will  be  practi- 
cally correct,  provided  the  optical  and  reducing  constants 
nsed  are  based  on  the  factor  .00386.  For  instance,  the 
specific  rotation  of  maltose  is  138°,  but  as  its  density  factor 
for  a  10  per  cent  solution  is  .00393,  its  specific  rotation  for 
the  factor  .00386  (symbolyzed,  [a]^^)  is  fff  x  138,  or 

I3S.50. 
The  equations  with  these  constants  become  : 


i.  (i) 

53.0  />+  135.5  »*  +  195  A  =  a^386.  (2) 

Z>+.6i^  =  K386.  (3) 

(The  per  cents  are  given  as  decimals  by  these  equations.) 
In  1897  Brown,  Morris,  and  Millar  published  curves 
giving  the  density  factors  of  most  of  the  common  hexose 
carbohydrates  and  starch  derivatives  of  malt  conversion, 
calculated  from  results  obtained  by  evaporation  of  solu- 
tions in  vacuo  over  phosphorus  pentoxide.  Similar  work 
was  done  in  1889  on  acid-hydrolyzed  starch  products  at 
the  sugar  laboratory  of  the  Massachusetts  Institute  of 
Technology,  so  that  the  true  density  factors  are  now  well 
established  for  pure  products  of  acid  and  diastase  con- 
verted starch. 

As,  however,  the  density  factors  differ  with  the  degree  of 
conversion,  and  as  this  latter  is  measured  most  conveniently 
and  rapidly  by  the  specific  rotatory  power,  it  is  most  con- 
venient to  obtain  first  this  value  as  expressed  by  the  factor 
.00386  in  calculating  the  absolute  value. 


STARCH   AND    STARCH    PRODUCTS  1 93 

Determination  of  Specific  Rotatory  Power.  —  The  density 
of  the  filtered  solution  of  the  hydrolyzed  product  (which 
should  approximate  to  1.04)  is  determined  as  accurately 
as  possible  at  15.5°.  The  solution  is  then  polarized  in  a 
2-decimeter  tube,  most  conveniently  in  a  quartz-wedge 
saccharimeter  provided  with  a  yellow  light  screen,  either 
of  bichromate  solution  or  a  piece  of  brown  glass.  The 
saccharimeter  reading  is  multiplied  by  the  "  light  factor  "  of 
the  instrument  for  hydrolyzed  starch  (discussed  in  a  later 
chapter)  which  is  .345.  The  saccharimeter  reading  multi- 
plied by  this  coefficient,  which  is  the  equivalent  of  one  sac- 
charimetric  division  in  angular  degrees  of  rotation  of  the 
plane  of  polarization  of  the  standard  yellow  ray,  gives  a  of 
the  equation  :  av 

hv 

Since  w  in  100  (Mohr)  cubic  centimeters l  = — —.the 

.00386 

equation  becomes,        a, 386  =  '345  ^10^.00386) 

Expressing  the  constants  by  a  four-place  logarithm,   the 
calculation  for  a/>  386  becomes  : 

a  =  log.  /L -f  colog.  (d—  i)  +  8.8234—10. 

The  density,  especially  in  acid-hydrolyzed  products,  must 
be  corrected  for  the  influence  of  the  dissolved  mineral  mat- 
ter. This  is  done  by  taking  20  cubic  centimeters  of  the 
solution,  evaporating  practically  to  dryness  in  a  tared  plati- 
num dish,  and  then  incinerating  in  a  "low  temperature" 
muffle,  a  little  vaseline  being  added  to  prevent  excessive 
swelling  of  the  coal.  The  ash  is  weighed  to  .0001  gram, 

1  The  density  standard  is  15.5°  C,  the  polarimetric,  20°  C. 
o 


194  STARCH   AND    STARCH    PRODUCTS 

and  .008  is  deducted  from  the  density  for  every  gram  pres- 
ent in  100  cubic  centimeters  of  the  original  solution. 

For  factory  control  in  the  manufacture  of  glucose,  and  in 
commercial  work  where  great  accuracy  is  not  needed,  the 
Brix  spindle  can  be  used,  the  reading  of  which  giving  per 
:ent  of  solids  (grams  in  100  grams)  must  be  applied  in  the 

..ormula,  a=  ,  the  Brix  reading  being  taken  as  /;  d 

being  found  from  the  Brix  comparison  table.  Since  the 
density  at  which  the  optical  and  reducing  constants  have 
been  calculated  is  approximately  1.04,  it  is  clear  that  an 
error  of  .1  Brix  (about  .0004  in  density)  makes  an  error  of 
i  per  cent  in  the  result.  Hence  the  ordinary  Brix  spindle 
is  not  sensitive  enough  for  highest  accuracy.  In  com- 
mercial glucoses,  the  influence  of  the  mineral  matter  also 
lowers  the  result  from  i  to  2  per  cent.  The  uncorrected 
values  are,  however,  sufficiently  approximate  to  be  valuable 
for  commercial  work  in  determining  the  composition  of 
the  product.  The  calculation  in  this  case  becomes  : 

log.  R  +  colog.  /  -f  colog.  d+  1.2367. 

The  true  specific  rotation  ,  for  the  actual  weight  of  i 
gram  of  carbohydrate  in  i  true  cubic  centimeter,  can  be 

7? 

calculated  from   [a]/,^  by  multiplying  by  .99802 


.00386, 

the  first  factor  being  that  for  conversion  of  the  values  from 
concentrations  representing  densities  taken  at  15.5°,  re- 
ferred to  Mohr  cubic  centimeters  at  15.5°,  to  densities  at 
15.5°  referred  to  true  cubic  centimeters.  The  factors  for 
conversion  of  [a]/)886  to  true  specific  rotatory  powers  of 
absolute  weights  of  carbohydrates  are  given  in  the  follow- 
ing table  : 


STARCH   AND   STARCH   PRODUCTS 


195 


DENSITY  FACTORS  FOR  REFERENCE  TO  ACTUAL  WEIGHTS  OF 
ACID-HYDROLYZED  STARCH  PRODUCTS  IN  IOO  TRUE  CUBIC 
CENTIMETERS  OF  SOLUTION 


[«]l>386 

Density  fjlS^} 
factors  \    j5  5o/ 

Logarithms  of 
conversion  factors  l 

55° 

0.003837 

9.9965 

60° 

0.003844 

9.9973 

65° 

0.003850 

9.9980 

7o° 

0.003857 

9.9988 

75° 

0.003864 

9.9996 

80° 

0.003870 

0.0002 

85° 

0.003877 

O.OOIO 

90° 

0.003884 

O.OOI8 

95° 

0.003890 

O.OO24 

100° 

0.003897 

O.OO32 

105° 

0.003904 

O.OO4O 

110° 

O.OO39II 

O.OO48 

115° 

0.003918 

0.0056 

120° 

0.003925 

0.0063 

I25° 

0.003931 

O.OO7O 

130° 

0.003938 

O.OO78 

135° 

0.003945 

0.0085 

I400 

0.003951 

O.OO92 

145° 

0.003958 

O.OIOO 

150° 

0.003965 

0.0107 

155° 

0.003971 

0.0114 

160° 

0.003978 

O.OI2I 

165° 

0.003985 

O.OI29 

170° 

0.003991 

0.0136 

175° 

0.003998 

0.0144 

1  80° 

O.OO4OO5 

O.OI5I 

185° 

O.OO4OII 

0.0157 

190° 

O.OO40I7 

0.0164 

195° 

0.004023 

0.0170 

Mog. 


0.00386 


0.99802. 


196  STARCH    AND   STARCH   PRODUCTS 

In  conversion  of  K386  to  K  absolute,  since  the  cupric- 
reducing  power  of  pure  dextrose,  taken  as  i.oo  for  the 
factor  .00386,  is  .9915  in  absolute  value,  it  is  necessary  to 
add  the  cologarithm  of  this  number,  or  .0037,  to  the  loga- 
rithm of  the  conversion  factor  in  calculating  the  reducing 
power  in  terms  of  that  of  the  equivalent  weight  of  detrose 
as  unity. 

Determination  of  the  Cupric-reducing  Power.  —  In  deter- 
mining the  cupric-reducing  power  of  hydrolyzed  starch 
products,  the  original  solution  must  be  diluted  sufficiently 
to  give  about  .2  gram  of  copper.  With  the  Defren  method, 
this  means,  in  most  cases,  a  dilution  of  the  original  solu- 
tion to  £Q  of  its  original  concentration ;  taking,  for  in- 
stance, 25  cubic  centimeters  of  the  original  solution,  and 
diluting  to  500  cubic  centimeters.  Since  the  original  weight 
of  carbohydrate  is  determined  from  the  amount  in  100  cubic 
centimeters,  and  the  volume  of  the  solution  taken  for  the 
Defren-Fehling  test  is  25  cubic  centimeters,  the  copper 
reduced  by  the  amount  of  carbohydrate  in  the  original 
solution  is  obtained  under  these  conditions  by  multiplying 
the  actual  weight  by  80. 

The  calculation  is  expressed  by  the  following  equation : 

Cpe 

K__       
—  — > 

d—  I 
F 

where  p  is  the  ratio  of  the  concentration  of  the  original 
solution  to  that  of  the  solution  diluted  for  the  Fehling 
test,  e  is  the  "  dextrose  equivalent "  of  the  copper  as  given 
by  a  table  calculated  for  the  method  used,  and  C  is  the 
weight  of  copper  (or  its  oxide)  actually  weighed.  The 
actual  weight  of  carbohydrate  in  100  cc.  of  solution  is 


STARCH   AND   STARCH   PRODUCTS  197 

obtained  from  the  density  factor,  either  using  the  value, 
.00386,  as  has  been  customary  in  commercial  work,  or  the 
true  factor  obtained  from  the  determination  of  specific 
rotary  power  as  described. 

Diastase-converted  products,  such  as  beer  worts  or  malt 
products,  are  determined  in  an  analogous  way,  but  as  dex- 
trose is  usually  absent,  the  equations  expressing  the  primary 
constituents  are  modified  accordingly.  Moreover,  as  the 
malt  itself  contains  considerable  quantities  of  cane  and 
invert  sugars,  corrections  must  be  made  for  these  carbo- 
hydrates when  malt  extract  is  present  in  appreciable 
quantity,  and  the  determination  of  the  actual  carbohy- 
drate constituents  becomes  a  complicated  one.1 

Determination  of  the  Constitution  of  Hydrolyzed  Starch 
Products  from  their  Specific  Rotatory  Power.  —  As  already 
stated,  the  large  amount  of  experimental  data  on  acid- 
hydrolyzed  starch  products  obtained  under  many  diverse 
conditions  of  hydrolysis  points  to  the  important  con- 
clusion that,  in  acid  conversion,  products  of  the  same 
specific  rotatory  power  have  the  same  composition,  irre- 
spective of  the  source  of  the  starch,  the  nature  or  amount 
of  the  hydrolyzing  acid,  or  the  temperature  conditions, 
these  influencing  the  rate  of  hydrolysis  only. 

This  constant  relation  holds  true  only  with  products  of 
the  starch  itself  which  have  all  been  subjected  to  the 
same  conditions  of  hydrolysis,  and  not  to  mixtures  of 
products  at  different  stages  of  conversion  hydrolyzed 
under  different  conditions.  Moreover,  in  the  case  of 
products  hydrolyzed  with  acid  of  considerable  strength 

1  See  Moritz  and  Morris,  "Textbook  of  the  Science  of  Brewing,"  or  Heron's 
article  on  Sugar  in  Thorpe's  "  Dictionary  of  Applied  Chemistry,"  p.  669. 


1 98 


STARCH  AND  STARCH  PRODUCTS 


or  at  high  temperature,  there  are  always  some  decompo- 
sition or  so-called  "reversion"  products  formed  to  some 
extent.  These  introduce  some  error  in  the  higher  con- 
verted products.  The  nature  and  conditions  of  forma- 


200        190       180        170        160        150        140        ISO        120     -410       TOO         90         80          70         fiO  >  5C 

00 

52.7 

^'[CPlD  ' 

=  1.0 

OK. 

^Pr 

..\ 

* 

-.80 

i 
j 

;  .70 

< 

! 

~    60 

^  '- 

+ 

^ 

+ 

'^ 

^ 

s+ 

.•/ 

'/ 

X 

A    -W 
) 

0 
£ 

J 

^  .30 

s 

'S 

^x 

; 

S. 

+ 

. 

S- 

s 

*' 

/ 

'  ' 

/• 

.10 
0 

+  + 

/- 

£ 

•^ 

Thei 
202.  fc 

°r^]n) 

Specific  Rotation (CfC]D) 

FIG.  32.  —  CURVE  OF  RELATION  OF  CUPMC-REDUCING  POWER  TO  SPECIFIC 
ROTATION  OF  ACID-HYDROLYZED  STARCH  PRODUCTS.1 


tion  of  these  products,  which  under  ordinary  conditions 
are  present  only  in  very  small  quantities,  are  by  no  means 
thoroughly  understood.  In  many  cases,  there  seems  to 
be  a  slight  loss  in  carbohydrate  from  the  breaking  up  of 

1  The  dots  and  crosses  represent  reducing  values  actually  obtained  by 
experiment,  the  crosses  being  results  from  products  separated  by  alcoholic 
precipitation. 


STARCH  AND  STARCH  PRODUCTS 


199 


the  molecule  through  oxidation.  As  a  rule,  these  bodies 
are  present  in  negligible  quantities. 

Brown,  Morris,  and  Millar  have  published  the  results  of 
over  five  hundred  analyses,  conclusively  proving  that  the 
law  of  constant  relation  between  optical  rotation  and 
cupric  reduction  does  exist  in  diastase-conversion  prod- 
ucts of  starch. 

The  relations  between  optical  rotation  and  cupric  reduc- 
tion of  products  of  the  two  kinds  of  hydrolysis  are  graphi- 
cally shown  in  the  preceding  diagram. 

From  the  values  thus  obtained,  by  calculation  by  the 
equations  given  on  page  192,  the  following  curves  have 
been  plotted,  which  show  the  per  cent  of  primary  con- 


IUU 

90 
1  70 

£ 

I50 

<30 
£20 

Sio 

0 

I 

-3 

I 

/ 

IUU 
9O 
80 
70 
60 
50 
40 
30 
20 
10 
O 

/ 

V 

Ss 

f 

*' 

A 

*$*— 

\\ 

V 

\ 

t 

/$ 

\v 

s 

/ 

/  \ 

\ 

><r 

*~  — 

—  —  , 

4 

of'' 

/ 

\ 

\ 

\ 

. 

/ 

^ 

. 

4 

7 

\ 

^ 

<\ 

s 

\ 

/ 

^ 

y 

^ 

^ 

N 

\ 

/ 

^ 

^ 

v>^ 

—  . 

—  -  — 

* 

S 

195C 

b 

190         170          150         130         110          90            7O           50 

SPECIFIC  ROTATI 


FIG.  33.  —  RELATION  OF  THE  CARBOHYDRATE  CONSTITUENTS  OF  ACID  AND 
DlASTASE-HYDROLYZED  STARCH  PRODUCTS  TO  THEIR  SPECIFIC  ROTATION. 


stituents  in  hydrolyzed  starch  products  (calculated  for  the 
factor  .00386).     The  dotted  lines  represent  the  products 
of  diastase  conversion  (see  Table  No.  5  in  Appendix). 
From  such  curves  the  constitution  of  any  pure  hydro- 


2OO  STARCH   AND   STARCH    PRODUCTS 

lyzed  product  can  be  determined  from  its  specific  rotatory 
power.  In  practice  there  are  comparatively  few  commer- 
cial products  pure  enough  to  permit  of  their  constitution 
being  determined  in  this  simple  manner.  In  the  case  of 
commercial  ''glucoses,"  however,  which  contain  but  traces 
of  foreign  substance,  this  method  is  most  valuable,  not  only 
in  factory  control,  but  for  valuation  of  different  lots  of 
product  for  the  purposes  for  which  the  glucose  is  to  be  used. 

Manufacture  of  Commercial  Glucose  and  Grape  Sugar.— 
The  word  "glucose"  is  used  to  mean  different  things,  and 
consequently  there  is  considerable  misunderstanding  as  to 
what  is  meant  by  the  term.  In  Europe,  especially  Eng- 
land and  France,  the  word  is  synonymous  with  dextrose, 
or  "starch  sugar."  In  America  this  latter  product  is  in- 
variably called  "grape  sugar,"  glucose  being  applied  to 
the  thick  viscid  sirup  which  is  manufactured  in  large 
quantity  by  the  partial  hydrolysis  of  starch  with  acid.  It 
is  in  this  popular  signification  that  glucose  is  used  here. 
As  used  in  a  previous  chapter,  it  is  employed,  as  in  organic 
chemistry,  as  a  class  term  to  designate  a  group  of  hexose 
sugars. 

The  manufacture  of  glucose  is  carried  on  on  an  enor- 
mous scale  in  this  country,  in  conjunction  with  that  of 
starch  and  numerous  valuable  by-products,  which  latter 
will  only  be  alluded  to  in  the  following  description.1 

In  the  manufacture  of  "  glucose "  two  conditions  are 
imperative:  (i)  The  amount  of  dextrin  must  be  sufficient 
to  prevent  the  separation  of  crystallized  sugar  when  the 

1  Taken  from  a  paper  on  the  manufacture  of  brewing  sugars,  written  by 
the  author  and  George  Defren  for  the  North  British  Federated  Institutes  of 
Brewing  of  Manchester,  England,  in  1899. 


STARCH   AND    STARCH    PRODUCTS  2OI 

product  is  concentrated  to  45°  Be.,  or  about  84  per  cent. 
(2)  Under  similar  conditions  dextrin  should  not  separate 
out.  These  conditions  limit  the  conversion  stages  to  those 
represented  by  that  part  of  the  diagram  (Figure  33)  lying 
approximately  between  the  rotation  figures,  150°  and  100°. 
Commercial  glucoses  in  the  market  vary  in  polarization 
from  [a]  ^386=  145°  to  i?o°.  As  the  greatest  consumption 
of  glucose  is  in  the  manufacture  of  candies,  jellies,  and 
sirups,  its  composition  has  been  determined  by  the  de- 
mands of  these  trades.  The  use  of  glucose  in  beers, 
extensive  as  it  is,  takes  a  very  small  proportion  of  the 
total  output.  On  this  account  there  are  practically  two 
grades  of  glucose  on  the  market,  leaving  out  of  considera- 
tion goods  which  differ  only  in  concentration :  mixing 
(sirup)  glucose,  with  a  conversion  of  [a]/)386=  120°— 130° ; 
and  confectioners'  goods  of  [a] />»==! 30°— 140°.  The 
best  confectioners'  goods  are  commonly  about  [a]  #386  = 
135°.  There  is  by  no  means  a  rigid  standard,  however; 
in-  fact,  many  manufacturers  grade  according  to  the  per- 
fection of  refining,  the  clearer,  whiter  glucose,  independent 
of  its  conversion,  being  specially  treated  for  confectioners' 
use.  Jelly  goods  differ  from  mixing  glucose  merely  in 
concentration,  although  imperfectly  refined  candy  glucose 
is  often  worked  up  into  this  grade,  as  a  slight  turbidity 
or  tint  is  of  no  consequence  in  jelly  manufacture.  Mixing 
glucose  is  the  kind  usually  bought  by  the  brewer.  The 
composition  may  vary  through  wide  limits,  the  proportion 
of  dextrin,  for  instance,  varying  in  extreme  cases  about 
100  per  cent.  In  short,  the  commercial  grading  of  a  glu- 
cose is  no  criterion  of  the  relative  proportion  of  dextrose, 
maltose,  or  dextrin. 


2O2 


STARCH   AND   STARCH   PRODUCTS 


Space  permits  only  the  most  superficial  description  of 
the  manufacture  of  glucose.  In  general  the  process  con- 
sists of  three  parts  :  (i)  separation  of  the  starch  ;  (2)  con- 
version ;  (3)  refining.  (The  diagrammatic  scheme  (Fig.  34) 
will  assist  in  following  this  description.)  All  kinds  of  what 
is  known  as  No.  3  or  No.  4  corn  (maize)  are  used.  This 


(1A)   GERM  MEAL 


NEUTRALIStB 
BAG -FILTERS 

BONE  BLACK  FILTERS 

LE-EFFECT-EVAPORATO 

BONE-ELACK:FILTERS 


o 


VACUUM  PAN 


FIG.  34.  - 


(4)    FINISHED-GLUCOSE 

-DIAGRAMMATIC  SCHEME  OF  THE  MANUFACTURE  OF  COMMERCIAL 
GLUCOSE. 


corn  is  taken  from  the  cars  or  the  elevator  of  the  works 
to  the  steep  tubs,  which  hold  2000  bushels  or  more.  In 
steeping,  water  at  150°  F.  is  used  at  first,  then  the  steep  is 
allowed  to  cool  till  a  temperature  of  about  90°  F.  is  reached. 
Sulphurous  acid  is  used  to  prevent  putrefaction  and  assist 
softening.  The  steeping  lasts  from  three  to  five  days. 
The  separation  of  the  starch  consists  of  (i)  grinding  the 


STARCH   AND   STARCH    PRODUCT^  2O3 

wet  grain  mixed  with  water,  and  softened  by  steeping; 
(2)  separating  the  starch  grains  from  the  woody  fibre  and 
germ  by  washing  through  sieves  of  bolting  cloth,  rapidly 
shaken ;  (3)  settling  out  the  starch  from  the  gluten  by  sub- 
sidence while  passing  over  gently  inclined  runs  ("  tables  "). 
The  grinding  is  done  so  that  the  starch  grains  are  set  free, 
^ut  not  ruptured.  The  germ  is  removed  separately  in 
many  factories.  This  is  accomplished  by  coarse  grinding 
and  running  the  grain  mixed  with  much  water  through  a 
long  trough,  or  into  a  tank,  the  mass  being  agitated  slowly. 
The  germ  which  floats  is  carried  off  by  one  channel,  the 
rest  of  the  grain  by  another.  This  separation  of  the  germ 
is  an  important  improvement,  since  the  oil  which  is  con- 
tained in  it  (about  35  per  cent)  can  be  readily  obtained  as 
a  by-product,1  and  the  quality  of  the  glucose  is  much  im- 
proved by  its  removal.  The  grain  from  the  separators  is 
ground  and  washed  on  the  sieves  ("  shakers  ")  in  the  usual 
manner,  and  the  separated  liquor  sent  over  the  runs.  The 
thin,  highly  diluted  gluten  is  allowed  to  settle,  pumped 
through  filter  presses,  and  the  dried  cake,  which  contains 
over  30  per  cent  of  protein,  sold  for  cattle  feed. 

The  starch  collected  on  the  runs,  and  containing  about 
50  per  cent  of  moisture,  is  now  mixed  with  water  to  a  thick 
cream  of  about  20°  Be.,  preparatory  to  conversion.  Con- 
version is  carried  on  in  large  copper  boilers  at  a  steam  pres- 
sure of  30  pounds,  hydrochloric  acid  being  the  converting 
agent,  the  amount  used  being  about  .0006  of  the  weight 
of  the  starch. 

1  One  of  the  important  uses  of  corn  oil  is  in  making  "rubber"  floor 
matting.  Vulcanized  corn  oil  makes  an  excellent  rubber  substitute  for  such 
purposes.  It  is  also  an  adulterant  of  genuine  rubber. 


2O4 


STARCH   AND   STARCH   PRODUCTS 


In  some  factories  sulphuric  acid  is  still  used  as  the  hy- 
drolyzing  acid.  In  the  manufacture  of  candy  goods  and 
certain  hard  sugars  it  seems  to  have  some  advantages. 

Oxalic  acid  has 
been  used  for  the 
manufacture  of 
fine  candy  glu- 
cose. In  the 
manufacture  of 
grape  sugar  a 
much  larger  pro- 
portional amount 
of  acid  is  used, 
in  some  cases  up 
to  i  per  cent 


FIG.  35.  —  SECTION  OF  CONVERTER. 

A.  Perforated  steam  pipe.  D.    Acid  pipe. 

B.  Starch  liquor  pipe.  F.    Washout  pipe. 

C.  Discharge  pipe  to  neutralizer.  O.    Discharge  valve. 

V.    Air-vent  pipe. 
(From  Thorp's  "  Outlines  of  Industrial  Chemistry.") 


or    more    of    the 
weight  of  starch. 
The  point:  of  com- 
plete conversion  is  usually  controlled  by  the  disappearance 
of  the  dextrin  precipitate  when  the  liquid  is  poured  into 
alcohol. 

In  glucose  conversion  the  acid  is  mixed  with  about  fifty 
times  its  bulk  of  water,  and  is  run  into  the  "converter." 
Steam  is  then  turned  on  till  a  pressure  of  30  pounds  is  ob- 
tained. This  pressure  is  maintained  while  the  starch  milk 
is  pumped  in,  which  takes  about  half  an  hour.  Heating  is 
continued  after  this  for  40  minutes  or  more.  "  Dirty  " 
starch,  containing  much  gluten,  increases  the  time  of  con- 
version 10  minutes  or  more.  The  degree  of  conversion  is 
entirely  controlled  by  iodine  tests.  By  daily  practice,  work- 
men become  quite  expert  in  making  these  tests,  yet  from 


STARCH   AND   STARCH   PRODUCTS 


205 


week  to  week  there  is  apt  to  be  considerable  variation 
in  composition  when  tests  are  not  checked  by  chemical 
control  by  determining  the  specific  rotation  of  the  liquids 
from  the  bone-black  filters. 

The  refining  process  is,  in  general,  similar  to  that  of  cane 
sugar.  The  analogy  is  quite  close  in  the  case  of  the  solid 
grape  sugars.  In  the  case  of  glucose,  however,  there  is  a 
radical  difference  of  principle  which  must  not  be  over- 
looked. In  the  refining  of  glucose  the  purification  must  be 
carried  to  great  lengths,  at  least  as  far  as  color  and  ap- 
pearance are  concerned.  All  bodies  affecting  these  char- 
acteristics must  be  absolutely  removed  from  the  liquid,  or 
bleached  in  it,  since  there  is  no  mother  liquor  in  which  they 
can  be  deposited,  as  in  the  case  of  a  crystalline  sugar.  On 
this  account  the 
refining  of  glucose 
is  a  much  more 
delicate  process 
than  that  of  sugar. 

Neutralization 
is  an  important 
part  of  the  refin- 
ing, as  on  the 
thoroughness  with 
which  this  is  done 
depends  how  suc- 
cessfully the  albu- 
minoids, calcium, 
and  iron  salts  are  removed.  As  soon  as  the  conversion 
is  completed  the  liquid  is  blown  out  into  the  "  neutralizer," 
where  the  alkali,  usually  sodium  carbonate,  is  added.  In 


FIG.  36.  —  SECTION  OF  NEUTRALIZER. 

A .  Revolving  stirrer. 

B.  Sprinkler  pipe  for  alkaline  neutralizing  liquid. 

C.  Discharge  pipe  from  converter. 

(From  Thorp's  "  Outlines  of  Industrial  Chemistry.") 


206  STARCH   AND   STARCH   PRODUCTS 

many  factories  it  is  the  practice  to  cool  the  liquids  con- 
siderably before  neutralizing,  but  this  seems  unnecessary 
when  the  alkali  is  added  properly.  The  liquid  when 
neutralized  should  show  only  the  acidity  caused  by  carbon 
dioxide  or  the  weakest  vegetable  acids.  The  properly 
neutralized  liquid  is  clear  and  of  a  bright  amber  color, 
but  contains  large  flocculent  masses  of  coagulated  gluten, 
which,  in  a  test  tube  of  ordinary  size,  form  a  layer  about 
half  an  inch  thick.  When  the  proper  point  of  neutraliza- 
tion is  attained,  this  layer  is  greenish  drab,  owing  to  the 
precipitated  iron. 

As  in  sugar  refining,  the  precipitated  matter  is  removed 
by  bag  filters,  which  are  often  supplemented  by  a  press 
filtering.  In  the  case  of  highly  refined  glucoses,  precipi- 
tants  are  sometimes  used,  such  as  alum.  The  tendency 
seems  to  be  for  manufacturers  not  to  push  this  part  of  the 
refining  to  greatest  advantage,  but  rather  to  depend  on  a 
liberal  use  of  bone  black  to  do  much  of  what  it  would  seem 
could  be  accomplished  by  less  expensive  means  in  prelimi- 
nary clarification.  The  bone-black  treatment  is  quite  com- 
plicated, not  only  in  the  details  of  filtering,  but  in  the 
preparation  of  the  black.  Since  the  slightest  trace  of  alkali 
in  contact  with  hot  liquor  will  produce  a  brown  stain  of 
caramel,  removable  only  to  a  limited  extent  by  bone  black, 
the  black  itself  must  be  freed  from  all  traces  of  ammonia 
or  caustic  lime  by  a  careful  "  tempering "  with  hydro- 
chloric acid  or  some  similar  treatment,  and  subjected  to  a 
careful  washing  to  remove  soluble  salts  of  iron  and  calcium. 
The  glucose  liquors  are,  as  a  rule,  put  over  the  bone  black 
twice:  first  at  their  original  concentration,  about  18°  Be.; 
and  again  after  concentration  to  28-30°  Be.,  the  denser 


STARCH   AND   STARCH   PRODUCTS 


207 


sirup  going  over  the  freshly  tempered  black.  The  re- 
vivifying of  the  black  is  carried  out  on  lines  similar  to 
those  of  cane-sugar  refining. 
The  "  heavy  liquor  "  goes 
directly  from  the  filters  to 
the  vacuum  pan  in  most 
modern  factories.  Formerly 
a  preliminary  filtration  was 
necessary  to  remove  the 
calcium  sulphate  which  sep- 
arated out,  but  with  the  use 
of  hydrochloric  acid  con- 
versions and  neutralization 
with  soda  this  is  avoided. 
In  the  final  concentration 
sulphites  are  added  in 
amounts  varying  from  .008 

37.  —  SECTION    OF    BONE-BLACK 
FILTER. 

A .  Perforated  false  bottom  on  which  bone  black 

sulphites     is     as     follows :          «sts. 

B.  Discharge  pipe  for  filtered  liquor, 
(l)      tO       prevent       Oxidation     C.    Entrance  pipe  for  liquor. 

D.    Steam  pipe. 

and   consequent   coloration  E.  Air-vent  Pipe. 

,,  r-        •,  ,.  F,H,J,L.    Steam,  wash- water,  and  sewer  con- 

in    the    final    concentration          necdons. 

due  to  formation  of  caramel-  G'  °^^pe  **  Wash!"8  °U'  ™  *""* 

like    bodies,   and    Sometimes     ^,££.  Tank  connections,  coupled  by  hose 

ferric    SaltS'     (2}   tO    bleach*     (From  Thorp's  "  Outlines  of  Industrial  Chem- 
istry.") 

(3)  to  prevent  fermentation 

of  the  less  concentrated  finished  products,  as  the  thinner 
mixing  sirups  ;  (4)  in  candy  goods,  as  a  preventive  of  oxi- 
dation in  the  candy  kettle.  Confectioners'  goods  are  more 
heavily  "  doped  "  with  sulphites  than  others. 


to  .050  per  cent  SO2.  FlG- 

The    function    of    these 


208  STARCH   AND   STARCH    PRODUCTS 

The  refining  for  the  making  of  ordinary  commercial 
grape  sugar,  which  is  a  waxy  concrete  of  the  hydrated 
dextrose,  C6H12O6H2O,  and  partially  hydrolyzed  com- 
pounds, together  with  some  products  of  decomposition 
is  practically  identical  with  that  of  glucose.  The  con- 
centrated sirups  are  drawn  off  into  pans  or  barrels  and 
allowed  to  solidify,  a  "seed"  of  crystallized  sugar  often 
being  added  to  facilitate  crystallization.  Anhydrous  grape 
sugar  is  made  in  a  similar  way  from  a  sirup  which  is  re- 
fined at  lower  concentrations  throughout  the  process  in 
order  to  obtain  a  purer  product.  In  this  case  the  "  seed  " 
is  selected  with  the  greatest  care  from  absolutely  pure  an- 
hydride, all  hydrated  crystals  being  scrupulously  excluded. 
The  crystallization  is  complete  in  about  three  days,  when 
the  sugar  is  purged  in  centrifugals.  The  purged  liquors 
are  often  worked  up  into  the  "climax"  sugars,  a  dark 
product  used  by  brewers.  These  sugars  also  are  often  put 
on  the  market  as  "chips."  Glucose  sirups  are  usually 
made  at  five  concentrations:  41°,  42°,  43°,  44°,  45°  Be. 
Mixing  goods  are  usually  finished  up  at  41°  Be.  The 
higher  concentrated  products  are  confectioners'  or  jelly 
goods,  the  former  being  characterized  by  greater  perfection 
of  refining  and  a  large  amount  of  sulphites. 

As  to  the  manner  of  taking  concentration  determinations, 
the  glucose  manufacturers  do  not  use  the  same  scale  as  the 
sugar  refiners,  who  employ  Gerlach's  modification.  The 
glucose  scale  is  practically  identical  with  that  used  by 
the  alkali  manufacturers,  and  has  the  following  conversion 

formula  for  the  density  :  d=  — — Owing  to  the  great 

144  — Be. 

viscosity  of  glucose,  the  readings  are  taken,  not  at  the 


STARCH   AND   STARCH   PRODUCTS  2C>9 

scandard  temperature  of  the  instrument  (60°  F.),  but  at 
1 00°.  The  slightly  warmed  glucose  is  poured  into  a  cylin- 
der, preferably  of  glass,  which  is  placed  in  a  water  bath  at 
1 00°  F.  At  the  end  of  half  an  hour  or  so,  the  glucose  will 
have  reached  the  temperature  of  the  bath,  and  the  air  bub- 
bles will  have  escaped.  A  Beaume  spindle,  reading  to 
fifths,  is  then  cautiously  lowered  into  the  glucose  and 
allowed  to  come  to  equilibrium,  which  in  the  more  viscous 
samples  takes  some  minutes.  With  care  the  determination 
can  be  made  on  a  Westphal  balance.  All  samples  of  glu- 
cose should  be  tested  for  density,  as  the  viscosity  in  goods 
of  different  conversions  varies  to  a  marked  degree.  A  low- 
converted  sample  of  moderate  density  will  apparently  have 
much  more  "  body  "  than  a  high-converted  glucose  much 
more  concentrated. 

As,  apart  from  concentration,  the  quality  of  commercial 
glucose  is  largely  judged  by  its  appearance,  it  will  be  inter- 
esting to  consider  briefly  some  of  the  turbidities  and  colora- 
tions of  the  commercial  products,  their  causes,  and  actual 
influence  on  the  quality  of  the  glucose.  A  well-refined 
glucose  is  practically  colorless  and  clear.  If  a  white  glass 
cylinder  is  filled  with  glucose,  the  color  of  the  sample  can 
be  seen,  as  well  as  any  turbidity.  If  the  color  is  a  pure 
white,  the  sample  is  dyed,  as  can  be  proved  by  exposing  it 
to  the  light  for  a  few  days,  although  this  coloring  is  rarely 
done  so  well  that  a  close  inspection  will  not  reveal  the  violet 
tint.  As  all  glucoses  darken  slightly  on  exposure  to  the 
light,  the  color  balance  soon  becomes  disturbed,  and  the 
presence  of  the  dye  is  made  more  evident.  If  no  dye  is 
present,  the  glucose,  unless  quite  turbid,  will  show  some 
color,  usually  green  or  yellow.  These  tints  are  almost 


210  STARCH   AND   STARCH   PRODUCTS 

invariably  present,  and  seem  to  be  caused  by  traces  of  iron 
salts  and  vegetable  coloring  matters.  They  are  of  little 
consequence,  except  as  indicators  of  the  thoroughness  of 
the  refining,  and,  hence,  of  the  removal  of  albuminoids 
and  oil.  A  reddish  brown  discoloration  is  the  result  of 
excess  of  alkali,  as  a  rule  either  through  imperfect  neutral- 
ization or  defective  treatment  of  bone  black. 

Cloudiness  caused  by  faulty  conversion,  separation  of 
dextrins  in  one  case  or  sugar  in  the  other,  is  in  these  days 
of  rare  occurrence.  A  smoky  appearance  is  often  caused 
by  bone-black  dust,  or  in  some  cases  from  iron  sulphide, 
when  a  large  quantity  of  new  black  is  used  in  refining ; 
these  faulty  results,  of  course,  are  from  improper  prepara- 
tion of  the  black.  White  cloudiness  is  usually  caused  either 
by  calcium  salts  or  by  organic  growths  due  to  fermentation. 
The  former  may  be  sulphate  or  phosphate.  Sulphates  in 
goods  converted  by  hydrochloric  acid  are  in  the  main  in- 
troduced through  use  of  impure  acid,  or  in  sulphite  liquors ; 
phosphates,  from  excess  of  "tempering  acid,"  or  incomplete 
washing  of  the  black.  The  clouds  due  to  fermentation, 
which  naturally  are  more  common  in  goods  made  in  hot 
weather,  are  usually  the  result  of  storing  thin  liquor  (in 
process)  at  too  low  a  temperature.  Of  course  the  fermen- 
tation organisms  can  easily  be  identified  by  the  microscope. 
A  quick  way  of  identification  is  to  acidulate  the  sample 
with  hydrochloric  acid,  when  the  ferment  cloud  remains 
undissolved. 

Solutions  of  grape  sugar  show  the  same  characteristic 
colorations  and  turbidities,  in  a  greater  or  less  degree. 
Usually  they  show  caramel  tints,  owing  to  the  decomposi- 
tion products,  especially  in  inferior  goods. 


STARCH   AND   STARCH   PRODUCTS  211 

The  valuation  of  the  solid  starch  (grape)  sugars  is  practi- 
cally based  on  their  dextrose  content.  Whiteness  of  late 
years  seems  to  be  more  of  a  desideratum  than  formerly; 
hence  the  practice  of  dyeing  is  becoming  common.  The 
principal  mineral  impurity  objected  to  is  iron.  This  is 
rarely  present  in  more  than  traces.  A  delicate  test  for 
iron  in  sugars  or  glucoses  is  made  with  cochineal.  Sul- 
phites must  be  first  removed,  and  the  solution  made  neutral 
or  faintly  alkaline.  If  iron  be  present,  the  pure  crimson  of 
the  cochineal  gradually  passes  into  violet.  There  are  two 
commercial  grades  of  grape  sugar,  ordinarily,  "  seventy  " 
and  "eighty"  sugar,  the  numbers  referring  to  the  assumed 
dextrose  content. 

A  "glucose  "  of  high  quality,  made  by  primitive  methods 
by  conversion  of  the  starch  matter  of  rice  or  millet  by 
malt  infusion,  has  existed  in  Japan  for  centuries.1  This 
"midzu-ame"  (freely  translated,  "liquid  candy")  is  a 
transparent,  amber-tinted,  viscid  sirup,  much  resembling 
commercial  glucose  in  its  properties,  but  of  course  free 
from  more  than  the  merest  traces  of  dextrose.  In  short, 
it  is  essentially  a  pure  starch-conversion  product,  the  com- 
position of  which  can  be  determined  from  its  specific  rota- 
tion, analogously  to  such  determinations  of  acid-hydrolized 
glucose,  but  by  means  of  the  equations  applying  to  diastase 
conversions. 

Midzu-ame,  in  one  form  or  other,  has  long  played  a  very 
important  part  in  the  domestic  economy  of  Japan.  In 

1  Yoshida,  Chemical  News,  43,  29;  Skidmore,  "  Jinrikisha  Days  in  Japan," 
37  ;  Wiley,  Agric.  Science,  6,  57  ;  Storer  and  Rolfe,  Bull.  Bussey  Institu- 
tion, Harvard  Univ.,  3,  80 ;  Yei-Furukawa  (translation  by  Takaki),  ibid,9 
3»  95- 


212  STARCH   AND   STARCH   PRODUCTS 

some  measure  it  still  takes  the  place  which  sugar  occupies 
in  Western  nations.  It  is  of  peculiar  interest,  as  represent- 
ing an  advanced  development  of  a  sweet  barley  wort,  which 
must  have  been  used  to  considerable  extent  by  many  commu- 
nities of  Europe,  before  the  advent  of  cane  sugar,  which 
began  to  be  of  common  use  only  in  the  sixteenth  century. 

Manufacturing  Losses.  —  The  first  loss  in  manufacture 
occurs  in  the  soluble  matter  which  is  in  the  liquors  drained 
off  from  the  steep  tubs.  Practically  no  starch  is  lost, 
although  a  trace  is  found  in  the  steep  water,  from  oc- 
casional broken  grains,  but  there  is  a  considerable  loss  of 
valuable  food  materials,  —  carbohydrates,  oil,  and  albumi- 
noids. In  many  places  it  has  been  found  profitable  to 
recover  this  material  by  evaporating  the  steep  waters  in  a 
multiple-effect  to  a  thick  sirup,  and  adding  this  to  the 
gluten  meal  or  other  by-products  used  as  cattle  feed. 
The  steep  waters  contain  5  to  6  per  cent  of  this  soluble 
food  matter,  and,  moreover,  make  an  offensive  sewage  if 
allowed  to  run  into  a  stream. 

The  corn  itself  is  graded  largely  on  the  moisture  it  con- 
tains. According  to  Archbold,  the  average  composition 
of  "  No.  4  "  corn,  the  kind  usually  used  in  starch  and  glu- 
cose manufacture,  is : 

Oil 5.20  per  cent 

Carbohydrates  (Starch,  54.8  per  cent)  71.22 

Albuminoids  ("Gluten")          .         .  10.46 

Ash 1.52 

Water n.6o 

The  next  loss  of  starch  occurs  in  the  bran,  or  "  wet  feed," 
the  amount  found  here  being  a  measure  of  the  efficiency 


STARCH   AND   STARCH   PRODUCTS  2 1 3 

of  the  removal  of  the  starch  from  the  cells  of  the  grain  in 
the  mechanical  separations,  and  incidentally  of  the  steeping. 

Determination  of  starch  in  the  gluten  liquors,  passing 
off  from  the  "  runs  "  or  "  tables  "  for  depositing  the  starch, 
shows  the  amount  passing  away  in  the  gluten.  This  may 
vary  considerably  according  to  the  efficiency  of  the  steep- 
ing, and  also  very  largely  to  the  skill  of  the  "  paddlers," 
workmen  who  keep  the  surface  of  the  deposited  starch 
clean,  and  the  stream  of  starch  and  gluten  flowing  slowly 
and  evenly  down  the  runs.  These  men  prevent  the  par- 
tially coagulated  gluten  from  accumulating  at  any  point,  and 
remove  the  occasional  accidental  obstructions  which  effect 
serious  loss  of  starch  by  causing  currents  to  cut  into  the 
deposited  mass.  The  starch  lost  in  the  gluten  liquors  may 
amount  to  from  20  to  70  pounds  per  1000  gallons.  This, 
however,  is  saved  in  the  by-product  (gluten  meal),  and  to 
some  extent  is  necessary  to  facilitate  the  filtering  in  the 
gluten  filter  presses. 

With  the  exception  of  a  small  amount  of  starch  possibly 
passing  into  the  germ  meal,  the  only  other  losses  in  starch 
manufacture  normally  occur  in  washing,  filtering,  and 
handling  the  product  in  the  kilns  and  packing,  and  are 
comparatively  small,  though  unavoidable. 

The  mechanical  losses  in  the  conversion  and  refining  of 
the  glucose  are  practically  the  same  as  in  sugar  refining. 
The  chemical  losses  are  much  less,  as  the  glucose  liquors 
do  not  hydrolyze  appreciably  under  the  conditions  of  re- 
fining. Aside  from  the  slight  decomposition  during  hydrol- 
ysis, already  referred  to,  the  only  source  of  destruction  is 
in  the  neutralizing,  where  portions  of  the  hot  liquor  may 
come  in  contact  with  an  excess  of  alkali  (sodium  car- 


214  '    STARCH   AND    STARCH    PRODUCTS 

bonate)  if  the  process  is  not  properly  carried  out.  In 
making  grape  sugar,  a  certain  amount  of  destruction  of 
sugar  is  inevitable.  Special  care  must  be  taken,  in  hot 
weather,  to  avoid  fermentation  of  thin  liquors  in  process. 
The  chemical  control  of  the  bone  black  is  practically  the 
same  as  in  sugar  refining. 

Valuation  of  Commercial  Corn  Starch.  —  In  general, 
starches  are  divided  into  three  grades,  alkaline  or  "  chemi- 
cal," acid,  and  neutral  starches,  according  to  the  reactions 
given  with  test  paper.  Alkaline  starches  are  those  in 
which  caustic  soda  has  been  mixed  before  running  on  the 
tables,  in  order  to  make  the  gluten  more  soluble  and  so 
effect  a  more  perfect  separation.  Acid  starches  were  origi- 
nally made  by  fermenting  the  gluten.  Neutral  starches, 
so  called,  are  made  by  use  of  sulphite  liquors  in  steeping 
and  running  the  starch,  the  usual  modern  method.  Ordi- 
nary starch  is  "  thick-boiling,"  making  a  stiff  paste  when  a 
5  per  cent  mixture  of  starch  in  water  is  heated  to  boiling. 
By  suitable  treatment  of  starch  with  dilute  acid,  at  temper- 
atures far  below  the  bursting  point  of  the  granule,  the 
starch  undergoes  a  gentle  hydrolysis,  and  becomes  "  thin- 
boiling,"  although  its  appearance  and  other  general  char- 
acteristics remain  unchanged.  Textile  manufacturers  for 
years  have  availed  themselves  of  this  property,  either  by 
heating  starch  with 'acetic  acid  or  other  weak  hydrolyte,  or 
by  allowing  the  moistened  starch  to  undergo  incipient  fer- 
mentation. Owing  to  the  greater  penetrating  power  of  the 
fluid  paste,  thin-boiling  starches  are  peculiarly  applicable 
in  sizing  or  stiffening  textiles,  as  a  large  amount  of  starch 
can  be  introduced  into  the  fabric  without  coating  the  sur- 
face. Consequently  the  viscosity,  or,  as  it  is  usually  stated 


STARCH   AND   STARCH   PRODUCTS  21$ 

iii  commercial  work,  the  "  fluidity,"  of  the  paste  which  the 
starch  makes  when  mixed  with  water  in  standard  propor- 
tion is  an  important  criterion  of  its  value  for  certain  pur- 
poses. These  fluidity  tests  are  made  in  various  ways,  but 
the  somewhat  crude  commercial  methods  depend  on  the 
number  of  cubic  centimeters  of  a  5  per  cent  starch  paste, 
made  by  rupturing  the  grains  with  a  weak  solution  of 
caustic  alkali,  which  will  run  out  of  a  funnel  through  a 
capillary  orifice  in  a  definite  period,  the  paste  being  at 
standard  laboratory  temperature,  and  the  instrument  ad- 
justed so  that  100  cubic  centimeters  of  pure  water  will  run 
out  of  the  instrument  under  the  same  conditions.  Thus, 
an  "80"  thin-boiling  starch  gives  a  paste  which  has  80 
per  cent  the  "fluidity"  of  water,  measured  in  this  way. 
A  more  accurate  method  of  measuring  fluidity  is  by  the 
Doolittle  torsion  viscosimeter,  which  measures  the  angular 
loss  in  the  oscillation  of  a  torsion  pendulum  whose  cylin- 
drical bob  is  immersed  in  the  paste.  The  supporting  wire 
is  first  twisted,  by  a  special  device,  through  an  angle  of 
360°,  and  the  pendulum  then  released,  the  difference  in 
reading  at  the  end  of  a  complete  oscillation  (the  reading, 
for  instance,  at  the  end  of  a  period  of  swing  to  the  right, 
and  the  reading  at  thfc  end  of  the  next  period  of  swing  to 
the  right,  neglecting  the  reading  at  the  end  of  period  of 
swing  to  the  left)  is  the  angular  measurement  of  the  loss 
due  to  retardation  by  the  viscosity  of  the  liquid.  These 
readings  should  be  checked  by  turning  the  wire  in  the 
opposite  direction,  and  taking  a  new  set  of  readings.1  The 
instrument  is  usually  standardized  to  express  the  viscosity 

1  See  Gill's  "  Handbook  of  Oil  Analysis  "  for  a  more  complete  description 
of  this  instrument  and  manner  of  taking  measurements. 


2l6  STARCH    AND    STARCH    PRODUCTS 

in  terms  of  that  of  cane  sugar,  a  curve  being  plotted  to 
show  the  concentration  of  sugar  solutions,  giving  the  vis- 
cosities expressed  by  the  angular  retardations.  With  the 
Doolittle  viscosimeter,  readings  can  be  taken  at  any  con- 
venient temperature,  as  there  is  a  water  or  oil  jacket  by 
which  the  test  solution  can  be  heated. 

Moisture.  —  Starch  under  normal  atmospheric  condi- 
tions contains  12-18  per  cent  of  moisture,  according  to  its 
origin.  This  can  be  driven  put  by  drying  at  105°  C,  but 
the  dried  product  is  extremely  hygroscopic  and  rapidly 
takes  up  moisture  to  the  normal  amount ;  for  instance, 
maize  starch  absorbs  about  12  per  cent,  potato  18  per 
cent,  which  cannot  be  entirely  removed  at  ordinary  tem- 
perature, even  by  shaking  with  alcohol.  In  fact  a  rapid 
method  of  moisture  determination  has  been  developed  for 
potato  starch  which  depends  on  the  removal  of  part  of  the 
water  by  alcohol.  This  will  remove  the  water  in  excess 
of  a  constant  percentage  (11.4).  If  the  starch  is  dry,  it 
will  take  up  water.  The  amount  absorbed  by  or  taken 
from  the  alcohol  is  determined  by  taking  its  density. 
A  table  has  been  prepared  by  Scheibler  which  gives 
the  per  cent  of  moisture  in  the  starch  corresponding 
to  the  density  of  the  alcohol,  when  100  cubic  centi- 
meters of  alcohol  and  41.6  grams  of  starch  are  shaken 
together. 

Saare's  method,1  which  is  very  convenient,  and  precise 
enough  for  technical  purposes  (giving  results  for  potato 
starch  correct  to  .5  per  cent),  is  as  follows :  100  grams  of 
the  starch  are  washed  into  a  25o-cubic-centimeter  tared 
flask  and  made  up  to  the  mark  with  water  at  17.5°- 

1  Chem.  Zcit.,  52,  934. 


STARCH    AND   STARCH    PRODUCTS 


217 


From  the  weight  of  the  contents  of  the  flask,  the  moisture 
contained  in  the  original  starch  sample  is  determined  by 
the  following  table : 


WEIGHT  FOUND 

WATER  PER  CENT 

WEIGHT  FOUND 

WATER  PER  CENT 

289.40 

O 

277.20 

31 

289.00 

I 

276.80 

32 

288.60 

2 

276.40 

33 

288.20 

3 

276.00 

34 

287.80 

4 

275.60 

35 

287.40 

5 

275.20 

36 

287.05 

6 

274.80 

37 

286.65 

7 

274.40 

38 

286.25 

8 

274.05 

39 

285.85 

9 

273.65 

40 

285.45 

10 

273.25 

4i 

285.05 

ii 

272.85 

42 

284.65 

12 

272.45 

43 

284.25 

13 

272.05 

44 

283.90 

14 

271.70 

45 

283.50 

15 

271.30 

46 

283.10 

16 

270.90 

47 

282.70 

17 

270.50 

48 

282.30 

18 

270.10 

49 

281.90 

19 

269.70 

50 

281.50 

20 

269.30 

5i 

28I.IO 

21 

268.90 

52 

280.75 

22 

268.50 

53 

280.35 

23 

268.10 

54 

279.95 

24 

267.75 

55 

279-55 

25 

267.35 

56 

279.15 

26 

266.95 

57 

278.75 

27 

266.55 

58 

278.35 

28 

266.15 

59 

278.00 

29 

265.75 

60 

277.60 

30 

2l8  STARCH   AND    STARCH    PRODUCTS 

Commercial  starches  often  contain  an  excess  of  moisture. 
Whiteness  and  freedom  from  offensive  odor  or  taste  are 
necessary  qualifications  of  good  starch. 

Size  Compounds.  —  Starch  is  used  in  immense  quantities 
in  the  weaving  of  cotton  cloth  as  the  chief  ingredient  of 
size,  which  is  applied  to  the  warp  to  protect  the  threads 
from  chafing  during  the  weaving.  Other  material  is  added 
to  the  starch  to  make  the  size  flexible,  such  as  grease,  or 
calcium  chloride,  which  latter,  by  its  hygroscopic  action, 
prevents  the  size  becoming  brittle  and  brings  about  the 
same  result.  Copper  sulphate  or  zinc  chloride  (the  latter 
also  having  hydrolytic  influence)  is  added  in  small  quantity 
to  some  sizes  as  an  antiseptic  to  avoid  molding  or  mil- 
dewing. 

There  are  numerous  formulae  for  making  these  sizes, 
which  are  usually  prepared  by  the  mill  people  themselves, 
who  mix  the  size  ingredients  with  the  starch  paste ;  which 
latter  has  usually  been  put  through  some  primitive  process 
to  make  it  thin-boiling.  The  material  to  give  the  char- 
acteristic properties  to  the  size  is  usually  in  the  form  of 
"  size  compound,"  being  a  mixture  of  the  fatty  or  chemical 
ingredients  in  a  concentrated  form  in  starch  paste.  As 
the  starchy  material  is  unimportant  in  the  valuation  of 
these  size  compounds,  determinations  should  be  made 
of  the  fatty  or  chemical  ingredients. 

Dextrin  and  British  Gum.  —  The  term  "dextrin,"  like 
"glucose,"  is  a  much  overworked  one,  as  it  has  many 
significations.  As  already  referred  to,  the  numerous  inter- 
mediate products  of  starch  hydrolysis  which  can  be  pre- 
cipitated as  definite  compounds  by  alcoholic  fractionation 
are  known  as  dextrins;  but  these,  in  their  chemical  and 


STARCH   AND   STARCH    PRODUCTS  2IQ 

optical  behavior,  can  always  be  considered  as  molecular 
aggregates  of  a  primary  "dextrin,"  whose  characteristics 
are  well  denned  and  persist  in  all  such  compounds,  and 
the  hexose  sugars,  maltose  and  dextrose  (or,  in  the  case  of 
diastase-converted  products,  maltose  alone),  as  has  been 
explained.  "  Dextrin,"  as  used  in  commerce,  refers  to  a 
manufactured  product  of  variable  composition,  made  by 
heating  the  starch  to  about  170°  C.  A  certain  degree  of 
hydrolysis  is  effected  to  a  limited  extent  by  the  moisture 
and  acids  in  the  starch,  and  is  also  in  many  cases  produced 
by  moistening  the  mass  with  acid,  sometimes  hydrochloric, 
but  usually  nitric.  The  darker  products,  which  have  been 
subjected  to  a  more  prolonged  heating,  often  to  tempera- 
tures as  high  as  270°,  without  acid,  and  which  give  thicker 
mucilages  with  water,  are  known  as  "  British  gums,"  al- 
though there  is  no  hard  and  fast  distinction  between  these 
products  and  the  "dextrins."  These  "  torref action  dex- 
trins,"  as  they  have  been  called  to  distinguish  them,  are 
made  by  roasting  in  revolving  cylinders,  either  directly 
heated  by  a  furnace  or  by  an  oil  bath.  In  some  processes 
the  conversion  is  carried  on  in  metal  trays,  which  are 
placed  on  racks  in  a  kiln.  Color  and  "body  "  of  the  muci- 
lages which  these  products  make  with  hot  water  are  the 
principal  criterion s  by  which  they  are  judged.  A  good 
dextrin  or  British  gum  should  make  a  practically  clear 
solution  with  hot  water,  showing  none  of  the  pastiness  or 
colloidal  appearance  of  the  unconverted  starch.  These 
products  are  used  for  a  variety  of  purposes,  especially  in 
the  textile  industries,  as  well  as  for  mucilage,  gum  for 
postage  stamps,  labels,  etc.,  and  in  fact  for  all  purposes 
where  a  water-soluble  gum  is  needed.  There  are  no  fixed 


22O  STARCH   AND   STARCH    PRODUCTS 

rules  for  their  manufacture,  the  amount  of  heating,  acid, 
and  other  conditions  depending  on  the  peculiar  require- 
ments of  each  consumer.  Often  different  dextrins  are 
blended  to  obtain  the  requisite  quality. 

Chemically,  they  show  a  small  but  varying  reducing 
power,  which  is  much  less  than  corresponds  to  the  optical 
rotation  as  expressed  by  the  "law  of  relation"  of  an  acid- 
hydrolyzed  starch  product.  This  would  be  expected,  as 
not  only  are  products  formed  by  the  action  of  the  heat 
under  conditions  where  all  traces  of  water  are  absent, 
except  what  may  be  formed  by  the  decomposition  of  the 
molecule,  but  the  higher  converted  and  more  sensitive 
products  formed  in  the  preliminary  hydrolytic  action, 
which  always  takes  place,  are  to  considerable  extent 
destroyed  and  converted  into  caramel  bodies. 

A  determination  of  the  specific  rotation  of  a  torrefaction 
dextrin,  however,  in  connection  with  the  cupric-reducing 
power,  often  throws  valuable  light  on  the  conditions  of  its 
manufacture.  Viscosity  tests  are  most  useful  in  the  valua- 
tion of  a  dextrin,  speaking  generally,  but  the  peculiar  use 
for  which  the  dextrin  is  designed  often  demands  special 
requirements.  Starches  of  different  kinds  also  give  differ- 
ent qualities  of  dextrin.  Most  of  these  dextrins  and  Brit- 
ish gums  are  in  the  form  of  powders,  which,  if  freshly 
made,  will  show  under  the  microscope  the  form  of  the 
original  starch  grains  from  which  the  product  has  been 
obtained.  Some  forms,  as  "gommelin,"  are  in  the  state 
of  glassy  grains  much  resembling  gum  arabic,  and  are 
fairly  pure  hydrolyzed  products.  Starch  "  pastes  "  are  made 
by  a  gentle  hydrolysis,  usually  with  acetic  acid,  and  then 
thickened  with  borax,  which  makes  a  very  stiff  mass. 


STARCH   AND   STARCH    PRODUCTS  221 


SOME  PAPERS  ON  STARCH  AND  ITS  DERIVATIVES, 
BEARING  ON  SUBJECT7MATTER  OF  PREVIOUS 
CHAPTER 

Musculus  and  Gruber.  —  Bull.  Soc.  chim.  (2),  30,  54. 

Bondonneau.  —  Compt.  rend.,  81,  972;  Bull.  Soc.  chim.  (2),  28,  452. 

O'Sullivan. — J.  Chem.  Soc.  (London),  25,  579;  29,  479;  30,  125. 

Wiley.  — Proc.  A.  A.  A.  S.,  30,  65. 

Brown  and  Heron.  —  Ann.  Chem.,  199,  242  ;  231, 125  ;  J.  Chem.  Soc. 
(London),  35,  596. 

Saloman.  —  J.  pr.  Chem.  (2),  28,  82. 

Schulze.  —  Ibid.  (2),  28,  311. 

Brown  and  Morris. — J.  Chem.  Soc.  (London),  47,  52'7  ;  53,  510;  55, 
449;  63,  604. 

Brown,  Morris,  and  Millar.  — Ibid.,  67,  830  ;  71, 72  ;  75,  286 ;  75,  308. 

Brown  and  Glendinning.  —  Ibid.,  81,  388. 

Scheibler  and  Mittelmeier  —  Ber.  deut.  chem.  Ges.,  23,  3060. 

Lintner  and  Dull.  — Ibid.,  26,  2553. 

Ling  and  Baker. — J.  Chem.  Soc.  (London),  67,  702. 

Rolfeand  Defren.— J.  Am.  Chem.  Soc.,  18,869;  (Revised :  Tech. 
Quart.,  10,  133). 

Rolfe  and  Faxon.  — Ibid.,  19,  698. 

Rolfe  and  Defren. — J.  Fed.  Inst.  of  Brew.,  5,  59;  Tech.  Quart.,  12, 
191. 

Rolfe  and  Geromanos. — J.  Am.  Chem.  Soc.,  25,  1003. 

Rolfe  and  Haddock.  — Ibid.,  25,  1015. 

Krieger. — Zeit.  Spiritusind.,  1894. 

Archbold.  —  J.  Soc.  Chem.  Ind.,  21,  4. 


MISCELLANEOUS   SACCHARINE   PRODUCTS 

Milk  Sugar.  —  Milk  sugar  (lactose)  is  the  only  other  biose 
sugar  which  is  produced  in  the  free  state  in  commercial 
quantities.  It  is  manufactured  almost  exclusively  from 
whey,  usually  obtained  as  the  by-product  of  cheese  factories 
or  other  curd  industries.  Whey  contains  about  5  per  cent 
of  lactose. 

Lactose  crystallizes  in  large  rhombic  crystals  as  the 
monohydrate  (C12H22On  •  H2O).  These  have  little  sweet- 
ness; in  fact,  pure  lactose  is  practically  tasteless.  It  is 
much  less  soluble  than  cane  sugar  or  maltose,  a  solution 
saturated  at  ordinary  temperatures  containing  no  more 
than  about  16  percent  of  it.  Its  specific  rotation1  is  52.5 
at  20°,  almost  identical  with  that  of  dextrose.  This  rota- 
tion value  is  not  affected  by  concentration,  but  is  changed 
considerably  by  temperature  variations.  Lactose  has  a 
cupric-reducing  power  of  .73.  It  is  readily  inverted  by 
hydrolytes  into  dextrose  and  galactose,  the  rotation  of  the 
invert  solution  being  increased  to  67°,  the  specific  rotation 
of  galactose  being  80°.  Concentrated  solutions  of  lactose 
after  prolonged  heating  for  several  days  become  distinctly 
sweeter  in  taste  from  the  inverted  products  formed.  Pure 
milk  sugar  can  be  made  by  precipitation  from  its  aqueous 
solutions  by  means  of  alcohol. 

1  After  previously  heating  the  freshly  dissolved  sugar  to  boiling. 


MISCELLANEOUS   SACCHARINE  PRODUCTS  223 

The  manufacture  of  milk  sugar  is  commonly  very  crude, 
consisting  in  evaporating  the  whey  in  open  pans  and  at 
the  same  time  carrying  on  a  clarification  with  alum.  The 
rough,  dark,  crystalline  product,  containing  much  mineral 
matter,  is  redissolved,  subjected  to  further  clarification,  and 
after  decolorizing  with  bone  black  is  evaporated  to  a  con- 
centrated solution  in  a  vacuum  pan,  and  allowed  to  crystal- 
lize gradually. 

Three  grades  of  milk  sugar  are  found  in  commerce : 
"  cobs,"  cylindrical  masses  formed  on  wooden  rods  im- 
mersed in  the  concentrated  sugar  liquors,  which  is  the 
purest  kind;  "plates,"  crystal  sheets  attached  to  the  sides 
of  the  tanks;  and  pulverized  sugar,  which  is  the  common 
form  in  which  it  reaches  the  consumer.  This  latter  is 
usually  made  from  the  loose  deposit  of  crystals  in  the  tank 
bottoms  by  grinding,  or  the  better  quality  from  the  "  cobs  " 
or  "plates."  This  pulverized  sugar  is  dried  in  a  kind  of 
granulator  before  it  is  packed. 

The  yield  of  milk  sugar  is  only  about  50  per  cent,  or, 
at  most,  60  per  cent,  of  that  contained  in  the  whey,  a  con- 
siderable loss  of  the  sugar  being  due  to  the  melassagenic 
salts  in  the  whey,  which  amount  to  nearly  15  per  cent  of 
the  sugar  content,  and  in  part  to  the  crude  methods  of 
preliminary  extraction. 

The  ordinary  refined  milk  sugar  of  commerce  contains 
usually  over  i  per  cent  of  mineral  matter,  but  owing  to  the 
fact  that  in  drying  it  is  partially  dehydrated,  samples  often 
polarize  over  100  per  cent  if  the  sample  is  tested  on  the 
saccharimeter,  using  the  appropriate  normal  weight. 

The  normal  weight  of  lactose  (L)  for  any  saccharimeter 
obviously  bears  a  ratio  to  the  sucrose  normal  weight, 


224  MISCELLANEOUS   SACCHARINE   PRODUCTS 

inversely  proportional  to  the  ratio  of  the  specific  rotations 
of  lactose  and  sucrose  respectively.  That  is, 

L  :N=66.$  :  52.72 

(52.72,  according  to  Landolt,  being  the  specific  rotation 
of  lactose  at  17.5°  C).  This  gives  32.856  grams  as  the 
normal  weight  for  the  standard  half-shade  saccharimeter 
using  Mohr  cubic  centimeter  flasks,  when  the  crystallized 
lactose  (monohydrate)  is  weighed,  the  solution  being  pre- 
viously heated. 

In  the  determination  of  lactose  in  milk,  owing  to  the 
bulk  of  the  precipitate  from  the  large  amount  of  albu- 
minoid matter  present,  volume  correction  must  be  made  by 
Scheibler's  method  of  "  double  dilution  "  already  described, 
or  the  solution  is  made  up  to  102.6  cubic  centimeters  if  the 
normal  weight,  26.048,  is  used. 

Wiley  recommends  the  use  of  an  acid  mercuric  nitrate 
solution  for  clarifying  solutions,  —  made  by  dissolving  mer- 
cury in  double  its  weight  of  nitric  acid  and  diluting  with  an 
equal  volume  of  water.  Usually  the  milk  is  measured  out 
by  a  pipette,  an  equivalent  of  two  or'  three  times  the  nor- 
mal weight  being  taken.1  About  3  cubic  centimeters  of 
clarifying  agent  is  used  for  the  normal  weight,  the  readings 
being  made  as  nearly  at  20°  as  possible,  as  the  specific  rota- 
tion of  lactose  varies  appreciably  by  change  of  temperature. 

Factory  experiments  have  shown  that  the  quality  and 
yield  of  milk  sugar  can  be  improved  by  application  of 
modern  sugarhouse  processes. 

Determination  of  Lactose  in  Mixtures  containing  Maltose. 
—  In  many  quasi-medicinal  food  preparations,  maltose  and 

1  Wiley,/.  Am.  Chem.  Soc.-iS,  428. 


MISCELLANEOUS   SACCHARINE   PRODUCTS  225 

lactose  are  present.  Boyden l  has  separated  lactose  from 
maltose  by  recourse  to  the  selective  action  of  a  yeast,  Sac- 
charomyce  anomolus,  which  totally  removed  the  maltose, 
leaving  the  lactose  unchanged.  The  lactose  was  then  de- 
termined by  the  Fehling  method. 

Honey.  —  Pure  honey  is,  in  the  main,  invert  sugar,  usually 
containing  also  a  small  quantity  of  sucrose,  waxy  matter, 
and  plant  extractives.  There  are  also  traces  of  formic 
acid  in  honey.  The  average  constitution  of  sixty  samples 
of  honey,  according  to  Sieben,  are : 

Dextrose,  34-71  per  cent 

Levulose,  39-24 

Sucrose,  1.08 

Organic  non-sugars,     5.02 
Water,  19.98 

Honey  varies  much  in  composition,  according  to  the 
food  of  the  bees,  as  the  insects  will  store  up  in  the  comb 
sugar  or  glucose  sirups  in  practically  unchanged  condition. 
Such  honey  is  usually  considered  as  adulterated,  just  as 
when  such  sirups  are  added  directly  to  the  product.  The 
chemical  determinations  of  honey  are  solely  directed  to 
ascertaining  its  genuineness  as  a  product  elaborated  by 
the  bees  from  the  blossoms.  The  amount  of  sucrose  in 
a  honey  rarely  exceeds  2  per  cent,  although  there  are  cases 
of  undoubtedly  genuine  honey  containing  more  than  5  per 
cent.  Hence,  the  determination  of  sucrose,  by  the  Clerget 
method,  is  a  valuable  criterion,  honey  containing  10  per 
cent  or  more  of  sucrose  being  unquestionably  adulterated. 
Lead  acetate  should  be  used  in  very  small  amount,  if  at 

1  Ibid.,  24,  993. 


226  MISCELLANEOUS   SACCHARINE   PRODUCTS 

all,  in  clarification.  Commercial  glucose  can  be  detected 
usually  by  the  same  method.  Advantage  has  been  taken 
of  the  temperature  effect  on  the  specific  rotation  of  invert 
sugar  to  detect  adulteration  by  commercial  glucose. 

As  already  stated,  the  specific  rotation  of  invert  sugar 
decreases  by  increase  of  temperature.  This  is  caused  by 
the  temperature  effect  on  the  levulose  alone,  its  specific 
rotation  decreasing  about  .638°  for  every  degree  increase 
in  temperature.  Authorities  differ  by  some  per  cent  as  to 
the  exact  value  of  the  specific  rotatory  power  of  levulose, 
which  is  approximately  —  93°  at  20°,  this  value  being  cor- 
rect enough  for  the  purpose.  At  about  88°  an  invert 
sugar  solution  becomes  optically  inactive,  owing  to  the 
specific  rotation  of  the  levulose  having  decreased  to  —  53°, 
and  hence  being  just  neutralized  by  the  dextrorotatory 
effect  of  the  equal  equivalent  of  dextrose  whose  specific 
rotation  is  53°. 

Chandler  and  Ricketts  have  utilized  this  property  of 
invert  sugar  to  detect  adulteration  of  honey  and  cane- 
sugar  sirups  by  commercial  glucose.  The  sample  of 
invert  sugar  is  heated  in  a  jacketed  tube  to  87°-88°  by 
means  of  a  current  of  hot  water  (or,  as  originally,  by 
a  heater  in  a  saccharimeter  specially  designed  by  the 
authors).1  If  only  invert  cane-sugar  products  are  present, 

1  The  invert-sugar  solution  must  be  neutralized  before  heating  to  87°  to 
avoid  any  hydrolysis  of  the  glucose.  Leach  advises  to  make  a  separate  solution 
for  this  test,  —  26.048  grams  of  the  sample  in  70  cubic  centimeters  of  water 
to  which  7  cubic  centimeters  of  acid  is  added.  The  solution  is  inverted  by  the 
usual  Clerget  process,  almost  neutralized  with  sodium  carbonate  or  hydrate, 
and  made  up  to  100  cubic  centimeters.  If  the  ordinary  commercial  saccha- 
rimeter is  used,  the  hot  tube  must  be  in  the  instrument  for  as  short  a  time 
as  possible  to  avoid  serious  errors  from  the  heating  of  the  saccharimeter. 

Leach  and  Lythgoe  find  that  the  specific  rotation  of  commercial  glucose 


MISCELLANEOUS   SACCHARINE   PRODUCTS  22/ 

the  reading  will  be  zero.  If  the  reading  shows  the  pres- 
ence of  commercial  glucose,  the  amount  can  be  approxi- 
mated closely  by  taking  the  specific  rotation  as  130°  and 
calculating  from  the  usual  equations  of  optical  rotation. 

Wiley  has  devised  a  method  for  determining  levtdose 
on  similar  principles.  He  uses  a  saccharimeter  specially 
designed  for  reading  solutions  under  different  temperature 
conditions,  and  determines  the  amount  of  levulose  in  100 
cubic  centimeters  by  the  standard  saccharimeter  readings, 
the  solution  being  made  up  so  that  there  is  approximately 
the  half  normal  weight  of  levulose  in  100  cubic  centi- 
meters of  solution.  Two  saccharimetric  readings  are 
taken  at  temperatures  about  50°  apart.  The  levulose 
present  is  then  given  by  the  following  equation : 

•p  TDf 

Per  cent  levulose  = 


.035/0  -/')ze/' 

where  R  —  R'  is  the  difference  in  the  reading,  and  t—f 
the  difference  in  temperature,  wf  being  the  weight  of  sam- 
ple dissolved,  and  .0357  the  difference  in  reading  caused 
by  one  degree  of  temperature  on  i  gram  of  levulose  in 
100  cubic  centimeters  of  solution. 

Maple  Sugar.  —  The  carbohydrate  of  maple-sugar  prod- 
ucts is  sucrose,  and,  consequently,  the  methods  of  analysis 
of  maple-sugar  products  are  identical  with  those  of  cane 
sugar. 


at  87°  is  diminished  about  7  %  of  its  value  at  20°  (yyV)  .  Leach  takes  the 
saccharimeter  reading  of  the  (sucrose)  normal  solution  of  commercial  glucose 
at  20°  C.  as  175.  This  corresponds  to  a  42°  Be.  commercial  glucose  [of  a 
specific  rotation  of  about  138°],  which  Leach  has  found  to  be  representative 
of  "  mixing  "  glucose.  At  87°,  the  saccharimetric  reading  was  found  to  be 
163. 


228  MISCELLANEOUS   SACCHARINE   PRODUCTS 

The  fact  should  not  be  lost  sight  of,  however,  that  what 
gives  maple  sugar  its  intrinsic  value  are  the  pleasantly 
flavored  plant  extractives. 

If  maple  sugar  is  refined,  it  becomes  nothing  more  than 
ordinary  granulated  sugar,  and  no  more  valuable.  Stimu- 
lated by  the  government  bounties  of  previous  years,  which 
were  based  on  the  sugar  content,  the  maple-sugar  pro- 
ducers have  worked  to  obtain  light-colored  sugars  with  high 
sucrose  content,  but  which  are  really  inferior  to  the  cruder 
products  on  the  flavor  of  which  the  true  value  of  the  sugar 
depends.  This  custom  of  valuing  maple  sugar  solely  on 
its  sucrose  content  has  led  unscrupulous  manufacturers  to 
adulterate  the  product  with  cane  sugar.  It  would  seem 
better  to  base  the  valuation  of  maple  sugar  on  a  ratio  of 
plant  extractives  characteristic  of  the  maple  to  the  sucrose 
content,  in  addition  to  the  sucrose  content  alone.1 

Maple  sirup,  so  called,  is  often  manufactured  from  com- 
mercial glucose,  cane  sirups,  and  an  extract  made  from 
hickory  bark  or  corncobs. 

Confectionery.  —  The  kinds  of  confectionery  are  so  vari- 
ous that  it  will  be  impossible  in  the  space  at  hand  to 
describe  more  than  the  general  characteristics  of  some 
common  products.  In  general,  candy  is  an  "  amorphous  " 
substance,  that  is,  it  does  not  tend  to  take  definite  crystal 
line  form,  but  can  be  molded  to  any  shape  desired.  Cane 
sugar  tends  to  crystallize  under  almost  every  condition  in 

1  See  Hortvet  (/.  Am.  Chem.  Soc.,  26,  1523),  who  bases  his  tests  for  adul- 
terants on  the  volume  of  the  precipitated  organic  matter  and  the  malic  acid 
content.  Hill  and  Mosher  have  suggested  a  somewhat  similar  method.  Jones 
determines  the  characteristics  of  the  ash.  Manganese  is  said  to  be  a  charac 
teristic  of  maple-sugar  ash.  This  characteristic  is  probably  dependent  on  loc"l 
soil  conditions,  however. 


MISCELLANEOUS   SACCHARINE   PRODUCTS  22Q 

concentrated  solution,  unless  strongly  melassagenic  bodies 
are  present,  but  by  melting  sucrose  crystals  at  160°,  and 
allowing  them  to  solidify,  an  amorphous  form,  "barley 
sugar,"  is  produced,  which,  however,  gradually  becomes 
crystalline.  If,  however,  a  sugar  solution  is  partially 
inverted,  the  highly  concentrated  residue  will  remain 
imorphous.  Hard  candies  were  originally  made  by  boil- 
ing sugar  with  some  inverting  agent,  commonly  cream  of 
tartar  or  tartaric  acid. 

Other  materials,  as  gums  and  clay,  have  been  used  in 
soft  candies  to  "  cut  the  grain  "  or  prevent  crystallization. 
"  Fondants,"  used  so  much  in  chocolate  creams  and  bon- 
bons, are  made  by  slightly  inverting  a  concentrated  solu- 
tion of  granulated  sugar  with  cream  of  tartar,  and  then, 
when  the  mass  is  of  the  right  concentration,  as  shown  by 
its  temperature  (about  255°  F.),  pouring  it  upon  a  cold 
slab,  and  beating  up  the  mass  till  it  cools.  In  this  way  a 
paste  of  fine  floury  crystals  is  formed,  which  remains  for  a 
long  time  in  this  condition  if  properly  made,  owing  to  the 
crystals  becoming  coated  with  invert  sugar  sirup,  which 
prevents  further  growth. 

In  modern  candy  making,  commercial  glucose  has  been 
found  to  be  an  ideal  material  for  "  cutting  the  grain,"  since 
the  20  per  cent  or  more  of  dextrin  contained  in  it  is  strongly 
melassagenic,  and  prevents  the  crystallization  of  several 
times  its  weight  of  sugar.  Glucose,  moreover,  is  a  health- 
ful sweet,  which  can  be  obtained  cheaply  in  great  purity. 
Hence  it  is  almost  a  universal  constituent  of  manufactured 
candies. 

A  large  class  of  candies  of  a  soft  rubbery  nature,  like 
" jujube"  and  other  pastes,  cheap  gumdrops,  and  the  like, 


230  MISCELLANEOUS   SACCHARINE  PRODUCTS 

are  made  by  boiling  commercial  glucose,  diluted  to  about 
35°  Be.,  for  about  three  hours  with  20-30  per  cent  of  its 
weight  of  starch  with  a  little  tartaric  acid,  or,  preferably, 
using  thin-boiling  starch.  This  class  of  confectionery  is 
known  as  "  AB  goods."  "  Marsh  mallows  "  are  made  from 
gelatin  beaten  up  with  glucose  and  starch. 

Aside  from  the  determination  of  coloring  matters,  flavor- 
ings, and  other  obvious  non-sugars  which  may  cover  nearly 
every  process  of  food  analysis,  the  principles  of  sugar 
analysis  given  in  the  previous  chapters  can  be  applied  to 
determining  the  composition  of  candies  in  general.  The 
Clerget  method  will  give  a  close  approximation  to  the 
unaltered  cane  sugar,  the  principal  error  being  a  small 
one  caused  by  the  hydrolyzing  action  of  the  inverting 
acid  on  the  glucose  and  other  starch  products.  By  deter- 
mination of  the  specific  rotation  of  the  separated  carbo- 
hydrate matter,  an  equation  can  be  formed  in  which  the 
effect  of  the  sucrose  is  known  and  the  glucose  and  invert 
sugar  expressed  as  unknown  quantities.  For  instance,  let 
5  be  the  per  cent  of  sucrose  determined  by  double  polari- 
zation, and  expressed  as  a  percentage  of  the  total  carbo- 
hydrate, x  being  the  per  cent  of  glucose  and  y  being  the 
per  cent  of  invert  sugar. 

Then,  x-\-y—  5=  per  cent  of  unknown  carbohydrate 

135^-937  +  66.5  S=a 

(135°  being  the  average  specific  rotatory  power  of  the 
carbohydrate  of  commercial  glucose). 

From  these  equations,  the  proportion  of  sucrose  (5) 
being  known,  the  invert  sugar  and  commercial  glucose 
carbohydrate  can  be  determined  with  sufficient  accuracy 


MISCELLANEOUS   SACCHARINE   PRODUCTS  231 

for  most  commercial  requirements.  If  starch  is  present 
in  a  conversion  state  much  less  advanced  than  glucose,  it 
may  be  necessary  to  determine  the  invert  sugar  directly, 
and  after  obtaining  the  total  weight  of  carbohydrate, 
determine  the  per  cent  of  starch  product  by  difference. 
The  specific  rotation  of  the  starch  product  obtained  by 
calculation  by  such  methods  will  be  indicative  of  the 
amount  that  the  starch  has  been  changed  in  the  making 
of  the  candy,  and  therefore  instructive  of  the  process  of 
manufacture. 

No  definite  rules  of  procedure  can  be  followed  in  the 
investigation  of  candies,  as  they  differ  so  widely  in  com- 
position and  properties.  In  any  attempt  to  get  at  the 
component  carbohydrates,  it  is  obviously  necessary  to 
eliminate  other  material  by  the  usual  processes  of  proxi- 
mate food  analysis.  Much  organic  material  of  the  nature 
of  albumen  can  be  removed  by  basic  lead  acetate,  but 
owing  to  its  influence  on  carbohydrates  other  than  sugar, 
especially  starch  products  and  invert  sugar,  it  is  better 
replaced  in  most  cases  by  aluminum  hydrate  mixture.  If 
the  carbohydrate  is  determined  by  the  density,  after  other 
organic  matter  has  been  removed,  ash  corrections  must  be 
made  on  the  solutions. 

It  is  clear,  as  in  most  proximate  analyses  of  complex 
commercial  products,  that  such  investigations  of  the  com- 
position of  a  candy  do  not  admit  of  high  accuracy,  but 
they  do  in  many  cases  throw  sufficient  light  on  its  make- 
up to  be  of  much  value,  in  fact,  to  meet  all  purposes  of 
such  work. 

Effective  application  of  the  many  methods  of  sugar 
analysis  will  usually  enable  the  well-informed  chemist  to 


232  MISCELLANEOUS   SACCHARINE   PRODUCTS 

get  the  desired  information  in  most  cases,  however  compli- 
cated the  confection. 

Jellies  and  Preserves.  —  Leach 1  uses  the  following  method 
for  approximately  determining  the  sugars  in  jellies,  pre- 
serves, and  similar  preparations : 

When  commercial  glucose  is  known  to  be  absent,  and 
the  sugars  consist  of  sucrose  and  the  invert  sugar  resulting 
from  the  former  by  the  cooking  processes  of  manufacture, 
a  double  polarization  is  made  by  Clerget's  method,  the  su- 
crose being  calculated  by  the  usual  formula  :  S  =  — 
(see  footnote,  p.  108). 

Inasmuch  as  the  actual  numerical  value  of  b,  the  reading 
of  the  (saccharimetric)  normal  solution  after  inversion  by 
the  Clerget  method,  is  due  to  the  sum  of  the  invert  sugar 
originally  present  in  the  sample  and  that  made  by  the 
Clerget  process,  the  ratio  of  the  reading  b  to  the  reading 
of  a  normal  solution  of  pure  sugar  completely  inverted  by 
this  process  will  express  the  per  cent  of  sucrose  (Sf)  in 
the  sample,  previous  to  any  inversion  in  the  process  of 
manufacture.  (This  per  cent,  of  course,  is  that  of  the 
finished  product,  not  of  the  total  weight  of  the  original 
ingredients  which  have  been  changed  in  manufacture.) 

Hence,  S'  =  —  — ,  since  —  44  +  .5  t  gives  the  reading 

—  44+. 5  t 
of  a  (saccharimetric)  normal  solution  completely  inverted 

by  hydrochloric  acid.  The  per  cent  of  invert  sugar  (/) 
actually  existing  in  the  manufactured  product  as  such  can 
be  determined,  according  to  Leach,  by  the  following  equa- 
tion:  /==I°5-3(^-^).  (The  factor,  105.3,  which  is  the 

—  44  +  -5  t 

1  Leach,  "  Food  Inspection  and  Analysis."  The  form  of  Leach's  equations 
are  changed  here. 


MISCELLANEOUS   SACCHARINE    PRODUCTS  233 

equivalent  of  invert  sugar  formed  from  100  parts  of  su- 
crose, must  be  used  because  the  value  l  —  44  -f  .  5  /  cor- 
responds to  the  invert  sugar  derived  from  26.048  grams  of 
sucrose,  and  not  to  26.048  grams  of  invert  sugar  already 
formed.) 

When  commercial  glucose  is  present,  Leach  determines 
the  amount  of  this  ingredient  by  polarizing  the  normal 
weight  of  sample  at  87°  as  described  on  page  226  (see 
also  footnote,  p.  226). 

Assuming  that  the  saccharimetric  reading  of  a  commer- 
cial glucose  solution,  26.048  grams  in  100  cubic  centimeters 
at  87°  C,  is  163,  since  the  invert  sugar  at  this  temperature 
is  optically  inactive,  the  per  cent  of  glucose  (G)  can  be 

a* 

found  by  the  equation,  G  —  -~-,  where  g  is  the  reading  at 

87°.  From  g  the  reading  g1  of  the  corresponding  amount 
of  glucose  at  the  laboratory  temperature  (20°)  can  be  cal- 
culated by  Leach's  factor,  -^f,  and  the  invert  sugar  in  the 

sample  by  the  equation,*  Im  lOS 


44  —  .5  / 

It  is  obvious  that  errors  may  be  introduced  by  the  heat- 
ing of  the  saccharimeter  in  taking  readings  at  87°  if  special 
care  be  not  taken,  or  a  specially  constructed  instrument  be 
used. 

A  definite  saccharimetric  value  is  assumed  for  glucose 
which  is,  as  has  been  shown,  a  product  variable  in  its 
composition  as  well  as  in  water  content.  The  glucose  ma) 

1  This  value  is  not  strictly  correct,  as  it  applies  to  the  rotation  of  an  inverted 
sucrose  solution  in  the  presence  of  hydrochloric  acid  which  increases  the  sac- 
charimetric reading.     The  reading  a  is  taken  before  adding  the  inverting  acid. 

2  A  simpler  equation  would  seem  to  be  :  1=  105.3  I  a~^~s  \  . 
See  footnotes  on  pp.  107  and  108.  \—  42+-5*/ 


234  MISCELLANEOUS   SACCHARINE   PRODUCTS 

change  during  the  manufacture  of  many  of  these  products, 
the  change  in  the  main  being  a  partial  dehydration.  If 
the  dehydration  be  sufficient  to  reduce  the  water  content 
of  the  product  below  that  in  the  original  glucose  (about 
20  per  cent),  it  is  clear  that  the  glucose  rotation  will  be 
changed  proportionately  to  the  (practically  anhydrous) 
sucrose  and  that  the  assumed  saccharimetric  value  of  175° 
will  not  apply  for  such  goods. 

Hence,  when  it  is  possible  to  remove  the  organic  matter, 
not  carbohydrate,  by  suitable  clarification  methods,  a  pro- 
cedure based  on  the  density  method  previously  described 
would  appear  to  be  more  accurate,  as  errors  due  to  dis- 
solved mineral  matter  can  be  eliminated  by  the  ash  correc- 
tion already  described.  Values  calculated  from  the  specific 
rotation  of  the  anhydrous  substance  are  not  affected  by 
variation  which  may  have  taken  place  in  the  water  content 
of  the  product. 

The  per  cent  of  total  solids  in  the  sample  can  be  obtained 
with  sufficient  exactness  for  calculating  the  proportions  of 
carbohydrates  in  terms  of  the  original  weight  of  sample, 
the  glucose  being  assumed  to  have  been  originally  an  80 
per  cent  solution.  If  the  weight  of  total  carbohydrates 
can  be  calculated,  reading  at  87°  is  unnecessary  for  deter- 
mining the  glucose  (see  p.  230).  Of  course,  as  in  Leach's 
procedure,  the  specific  rotation  for  the  anhydrous  glucose 
must  be  assumed. 

Hydrolyzed  Products  of  Cellulose.  —  Ever  since  1819, 
when  Braconnot  exhibited  sugar  made  from  linen  rags 
at  a  meeting  of  the  French  Academy,  cellulose  has  been 
considered  as  a  possible  material  for  sugar  production, 
but,  until  recently,  attempts  to  manufacture  sugar  or  gums 


MISCELLANEOUS    SACCHARINE   PRODUCTS  235 

from  wood  waste  economically  have  given  yields  so  low  as 
to  be  of  no  practical  value.  It  is,  nevertheless,  easy  to 
repeat  Braconnot's  work,  which  consisted  in  treating  the 
linen  with  about  twice  its  weight  of  sulphuric  acid  till  the 
whole  mass  became  a  paste,  and,  after  diluting  with  water 
to  about  a  2  per  cent  solution,  heating  for  ten  hours.  The 
neutralized  solution  on  evaporation  yielded  dextrose.  Any 
attempt  at  more  economical  production,  by  increasing  the 
proportion  of  cellulose  and  decreasing  acid,  results  in  an 
insignificant  yield.  The  practical  difficulty  seems  to  lie  in 
the  formation  of  insoluble  intermediate  products,  analogues 
of  dextrin,  which  are  only  broken  up  by  large  excess 
of  acid.  The  small  amount  of  soluble  product  formed  is 
optically  active,  its  specific  rotation  being  usually  about 
40°,  the  cupric  reduction  about  .90  as  found  in  experiments 
in  hydrolyzing  cotton  with  sulphuric  acid.1  This  corre- 
sponds to  a  mixture  of  xylose  (a  pentose  sugar  of  specific 
rotation  of  19.2°,  and  cupric-reducing  power  of  i.io)with 
dextrose,  but  the  data  at  hand  are  not  complete  enough  to 
be  conclusive.  Cross  and  Bevan  have  experimented  con- 
siderably on  the  hydrolysis  of  cereal  straws,  and  also  find 
pentose  sugars. 

Comparatively  recently,  Claassen  has  patented  processes 
for  conversion  of  cellulose  into  fermentable  sugar  by  which 
a  large  yield  is  claimed.  The  unique  and  vital  feature  of 
the  process  is  the  conduct  of  the  hydrolysis  under  mechani- 
cal pressure,  subjecting  a  mass  of  sawdust  moistened  with 
sulphuric  acid  to  the  action  of  a  press.  This  is  said  to  give 
soluble  saccharine  product  in  large  amount,  which  can  be 
utilized  in  the  economic  production  of  alcohol. 

1  Tech.  Quart,,  12,  51. 


236  MISCELLANEOUS   SACCHARINE   PRODUCTS 

Sugar  in  Urine.  —  In  certain  diseases  the  urine  is  found 
to  be  charged  with  sugar,  often  in  very  large  quantities. 
This  sugar  is  probably  dextrose,  although  there  is  evi- 
dence tending  to  show  that  levulose  and  other  sugars 
may  be  present.  The  determination  of  sugar  in  the  urine 
is,  therefore,  of  much  pathological  importance,  especially 
as  normal  urine  contains  none  or  but  occasional  minute 
quantities. 

The  polariscope  can  be  used  for  testing  urine  to  a  great 
extent,  in  the  advanced  stages  of  disease,  as  the  sugar 
content,  determined  as  dextrose,  may  amount  to  as  much 
as  10  grams  in  100  cubic  centimeters.  The  polarimetric 
values  are  not,  however,  absolutely  accurate,  as  normal 
urine  often  has  a  slight  negative  rotation,  corresponding 
to  a  reading  of  from  —.3  to  —.8.  According  to  Carles,1 
this  is  caused  by  a  complex  amine  compound  called 
"creatinin."  The  urine  is  filtered  and  polarized  directly 
in  a  2-decimeter  tube.  If  colloidal  albuminoids  are 
present,  which  make  the  filtrate  turbid,  and  which  are 
themselves  slightly  optically  active,  they  must  first  be 
removed  by  adding  a  few  drops  of  acetic  acid  and  heat- 
ing the  urine  nearly  to  boiling.  If  the  urine  is  very  dark 
and  turbid,  the  usual  clarifying  agent,  basic  lead  acetate, 
can  be  used.  In  this  case  allowance  must  be  made  for  the 
change  in  volume  caused  by  the  addition  of  the  clarify- 
ing agent ;  conveniently  by  the  use  of  the  double-marked 
flask,  as  already  described  in  discussing  quotient  of  purity 
determinations. 

If  the  commercial  saccharimeter  is  used  for  the  test,  the 
dextrose,  customarily  expressed  in  grams  in  100  (Mohr) 

1  Jour,  de  Pharrn.,  1890,  108. 


MISCELLANEOUS   SACCHARINE   PRODUCTS  237 

cubic  centimeters,  can  be  calculated  from  the  following 

RN' 
formula,  W=  -  ,  where  Nf  is  the  normal  weight  of  the 

instrument  for  dextrose.  As  the  normal  weights  for  su- 
crose and  dextrose  are  obviously  inversely  proportional  to 
their  respective  specific  rotations,  the  dextrose  normal  can 
be  easily  calculated.  Owing  to  the  effect  of  the  solvent 
on  the  specific  rotation  of  dextrose,  the  dextrose  normal 
weight  is  slightly  different  at  different  concentrations,  the 
specific  rotation  being  expressed  by  the  formula, 


For  the  standard  commercial  saccharimeter,  having  the 
sucrose  normal  weight  of  26.048  grams,  the  formula  for 

TT7     32.91  R 
urine  analysis  becomes  W  =  - 

100 

Saccharimeters,  both  of  the  rotating  and  the  quartz  com- 
pensation types,  are  made  specially  for  urine  analysis,  and 
are  graduated  to  read  directly  in  grams  of  dextrose  in  100 
cubic  centimeters.  As  these  instruments  do  not  differ  in 
essential  characteristics  from  the  standard  types,  details 
are  unnecessary. 

Copper  reduction  methods  also  apply  to  sugar  determi- 
nations in  urine,  providing  it  is  fresh.  If  the  urine  is 
ammoniacal,  obviously  the  modified  volumetric  method  of 
Pavy  must  be  used,  as  the  precipitated  cuprous  oxide  of 
the  Fehling  processes  will  be  dissolved  more  or  less  by  the 
ammonia. 


APPLICATION   OF  THE   POLARISCOPE   IN 
SCIENTIFIC    RESEARCH 

Laws  of  Optical  Isomerism.  —  In  the  opening  chapter, 
reference  was  made  to  the  important  theory  relating  optical 
activity  to  chemical  structure  which  was  developed  by  two 
independent  workers,  Van't  Hoff  and  Le  Bel.  Only  an 
outline  of  the  more  important  general  laws  developed  from 
this  theory,  that  may  be  necessary  for  a  comprehension  of 
the  chapters  following,  will  be  given  here. 

Theoretically,  any  substance  showing  optical  activity 
can  exist  in  at  least  three  isomeric  forms :  one  which  is 
dextrorotatory ;  another  of  equal  rotation  value  but  left 
rotating ;  and  the  third,  a  chemical  compound  of  equal 
equivalents  of  the  dextro-  and  levorotatory  isomers ;  this 
last  being  optically  inactive  and  termed  the  "racemic" 
form.  By  the  Van't  Hoff-Le  Bel  theory,  the  laws  relating 
the  molecular  structure  of  these  isomeric  forms  to  their 
optical  activity  can  be  expressed  by  the  following  graphical 
symbolism,  which  is  derived  from  that  commonly  used  to 
nterpret  the  chemistry  of  carbon  compounds. 

Most  optically  active  substances  can  be  symbolized  by 
one  of  three  schemes  of  configuration.  The  first  can  be 
generalized  in  the  form,  R— C  a  b — Rf,  R  and  RJ  repre- 
senting unlike  terminal  radicals,  and  C  any  number  (n)  of 
carbon  atoms,  each  carrying  the  unlike  radicals,  a  and  by 

238 


THE   POLARISCOPE   IN   SCIENTIFIC   RESEARCH         239 

and  connected  to  these  two  terminal  radicals  in  a  continuous 
chain.  The  number  of  different  symbolic  images  which 
can  be  made  by  varying  the  arrangement  of  the  univalent 
radicals  a  and  b  attached  to  the  intermediate  carbon  atoms 
(C)  determines  the  number  of  isomers  theoretically  possible. 

Those  figures  symbolize  optically  active  isomers  which 
show  an  arrangement  of  a  and  b  not  symmetrical  ("  asyiL. 
metrical")  to  the  carbon  chain;  that  is,  if  the -figures  arc 
divided  along  the  median  line  of  the  carbon  chain,  or 
bisected  horizontally,  the  two  halves  are  not  identical. 
Such  figures  can  be  grouped  in  pairs  which  represent 
arrangements  of  a  and  b  making  mirror  images  of  each 
other x  ("enantiomorphic").  The  images  so  related  typify 
isomers  which  have  many  physical  and  chemical  properties 
in  common,  but  which  rotate  the  polarized  rays  equally  in 
opposite  directions.  Such  isomers  are  said  to  be  "  antip- 
odal "  to  each  other. 

In  this  specific  scheme  of  configuration,  R — C  a  b — R* ', 
figures  which  show  symmetrical  distributions  of  a  and  b 
on  each  side  of  the  median  carbon  line  also  represent 
optically  active  substances,  there  being  no  representation 
of  optically  inactive  bodies ;  for  owing  to  the  unlike  termi- 
nal radicals,  the  figure  halved  horizontally  would  still  be 
asymmetrical.  Actually,  all  bodies  not  racemic  whose  prop 
erties  can  be  interpreted  by  this  graphical  representation 
have  been  found  to  be  optically  active. 

The  following  symbols  of  the  possible  isomers  of  ai\ 
optically  active  body  containing  five  radicals,  three  of  which 

1  The  assumption  is  made,  of  course,  that  a  and  b  are.  each  represented  in 
the  figure  by  some  symmetrical  character,  as  for  instance  a  by  a  dot  and  b  by 
a  circle. 


240         THE   POLARISCOPE  IN   SCIENTIFIC   RESEARCH 

are  "  asymmetric  carbon  atoms,"  will  illustrate  the  manner 
of  predicting  the  optically  active  isomers  : 


a  C  b    b  C  a 

a  C  b    b  C  a     a  C  b    b  C  a     a  C  b     b  C  a      b  C  a    a  C  b 
RJ         R'         R'         R1         R'         R1         R1        R' 

Those  which  are  paired  as  representing  "antipodes"  which 
can  form  racemic  compounds  are  joined  by  brackets. 
Consequently,  four  racemic  isomers  are  possible  in  com- 
pounds represented  by  this  scheme  which  contain  five 
carbon  atoms. 

By  the  mathematics  of  permutation  and  combinations 
the  possible  number  of  optically  active  isomers  (N)  which 
can  exist  according  to  such  a  scheme  can  be  computed  by 
N=  2n,  where  n  represents  the  number  of  "  asymmetric  car- 
bon atoms"  expressed  by  Cm  the  formula,  R  —  C  a  b  —  R  '. 

All  the  hexose  (glucose)  sugars  as  well  as  the  pentose 
and  other  carbohydrates  can  be  represented  in  this  scheme. 
For  instance,  from  an  elaborate  investigation  of  dextrose 
([a]/>=  52.7),  Fischer  has  symbolized  this  sugar: 

CH2OH 
HO  C  H 
HO  C  H 

H  C  OH 
HO  C  H 

CHO 

According  to  theory,  a  levorotating  isomer  should  exist 
whose  structure  can  be  symbolized  by  a  figure  the  mirror 
image  of  this.  Fischer  actually  isolated  a  left-rotating 


THE   POLARISCOPE   IN   SCIENTIFIC   RESEARCH         241 

sugar  which  has  many  of  the  properties  of  dextrose  and  a 
specific  rotation  of  --51.4.  Likewise,  many  other  antipo- 
des of  this  group  have  been  isolated  or  made  synthetically, 
so  that  of  the  sixteen  isomers  of  the  simple  hexose  sugars 
theoretically  possible  according  to  the  equation  N  =  2n,  a 
dozen  or  more  are  known. 

The  second  scheme  of  configuration  for  graphically  rep- 
resenting the  chemical  structure  of  optically  active  com- 
pounds is  expressed  as  R — C  a  b — R,  where  the  terminal 
radicals  are  alike  and  the  carbons  expressed  by  C,  to  which 
the  two  radicals  determining  optical  activity  are  attached, 

?,-i 
are  even  in  number.     In  this  scheme,  N=  2n~l  +  2*    ,  of 

5-1 

which   2n~l  represent  optically  active  isomers,  since  22 

figures,  having  symmetrically  distributed  a  and  b  groups 
relative  to  the  two  like  terminal  radicals  (as  shown  by 
dividing  such  figures  in  halves  horizontally)  are  optically 
inactive. 

Tartaric  acid  is  typical  of  this  group.  The  symbolic 
representation  of  this  acid  shows  two  "asymmetric  carbon  " 
groups.  Hence  there  are  two  possible  optically  active 
isomers  and  one  inactive.  These  can  be  represented  by 
the  following  symbols : 


COOH  COOH  COOH 

HO  C  H  H  C  OH  H  C  OH 

H  C  OH  HO  C  H  H  C  OH 

COOH  COOH  COOH 

The  first  two  are  antipodes,  in  combination  forming  the 
optically  inactive  racemic  acid.  The  third  (mesotartaric 
acid)  is  the  inactive  isomer,  as  predicted  by  the  equation. 


242         THE   POLARISCOPE   IN   SCIENTIFIC   RESEARCH 

The  third  scheme  of  configuration  representing  the 
isomerism  of  the  remaining  compounds  which  can  be 
symbolized  by  a  representation  of  a  chain  of  carbon  nuclei, 
is  identical  with  the  second  except  that  the  number  of  car- 
bon atoms  determining  the  asymmetric  groupings  (n)  is  odd. 
In  this  scheme  the  figure  can  be  halved  horizontally  on 
each  side  of  a  middle  carbon  group.  When  the  grouping 
of  the  radicals  expressed  by  a  and  b  is  symmetrical  rela- 
tive to  this  middle  carbon,  the  isomer  is  optically  inactive. 
The  total  number  of  optically  active  isomers  (N)  is,  in  this 
case,  N=  2n~l,  the  number  of  optically  active  being  ex- 
pressed :  «--i 
A  =  2n~l  -  2  2  . 

n-l 

The  inactive  isomers  obviously  are  expressed  by  /=  2  2  . 
Trioxyglutaric  acid  is  an  example  of  this  class. 

While  the  examples  cited  have  to  do  with  arrangements 
of  hydrogen  and  hydroxyl  radicals,  similar  arrangements 
of  other  radicals  also  represent  optical  activity,  the  essen- 
tial being  the  "asymmetric  carbon"  nuclei  which  permit 
of  configurations  which  are  mirror  images  of  each  other. 
So,  too,  optically  active  bodies  exist  whose  chemical  struc- 
ture can  be  explained  by  the  ring  representation,  character- 
istic of  the  so-called  aromatic  compounds.  These  can  be 
demonstrated  satisfactorily  only  by  a  solid  figure,  three 
dimensions  being  necessary.  The  asymmetric  carbons  in 
such  figures  are  best  represented  as  tetrahedra.  It  will 
suffice  to  state  here  that  when  the  substance  is  represented 
by  a  ring  structure  and  only  one  asymmetric  carbon  is 
present,  there  are  three  isomers,  two  of  which  are 
antipodes,  and  the  third  is  the  corresponding  racemic 
compound,  Many  constituents  of  the  essential  oils,  as 


THE   POLARISCOPE  IN   SCIENTIFIC   RESEARCH         243 

pinene,  limonene,  and  camphene,  are  represented  by  this 
configuration. 

If  two  asymmetric  carbons  are  in  the  ring  configuration, 
there  are  two  possible  antipodes  and  their  corresponding 
racemic  forms.  There  are  also  a  few  instances  in  which 
optical  activity  can  be  explained  by  figures  containing 
asymmetric  nitrogen  or  sulphur. 

In  natural  products,  as  a  rule,  only  one  or  the  other 
antipode  of  an  optically  active  substance  is  found,  rarely 
the  racemic  combination.  In  fact,  racemic  forms  of  many 
optically  active  substances,  as  starch,  are  unknown.  On 
the  contrary,  all  bodies  ordinarily  optically  active  in  the 
natural  state  are  inactive  when  made  by  synthesis  from 
inactive  substances.  This  is  due  to  the  formation  of  equal 
equivalents  of  the  antipodes  and  consequent  racemic  com- 
binations. In  order  to  separate  the  antipodes  of  such  syn- 
thetic compounds,  many  ingenious  chemical  and  physical 
methods  are  resorted  to. 

Antipodal  substances  show  identical  physical  and  chemi- 
cal characteristics  when  isolated  or  in  chemical  combination 
with  optically  inactive  substances,  if  certain  crystalline 
and  electric  peculiarities  (also,  in  some  cases,  physiological 
effects)  are  excepted. 

If,  however,  antipodal  substances  are  combined  with  an 
optically  active  body,  there  is  often  a  noticeable  change  in 
the  properties  of  the  compounds  formed  by  each  antipode. 
In  this  manner,  many  racemic  compounds  made  by  syn- 
thesis have  been  resolved  into  these  antipodes.  The  alka- 
loids have  proved  valuable  in  these  separations,  since, 
owing  to  the  difference  in  solubility  of  many  antipodal  salts 
formed  by  combination  with  these  bases,  many  isomers 


244         THE   POLARISCOPE   IN   SCIENTIFIC   RESEARCH 

can  be  separated  by  precipitation.  By  combinations  with 
the  alkaloids,  strychnine,  morphine,  brucine,  and  cinchonine, 
Fischer  was  enabled  to  obtain  optically  active  dextrose 
and  its  levo-isomer  from  the  optically  inactive  racemic 
body  synthesized  from  acrose.1 

Antipodal  isomers  have  also  been  separated  by  the  action 
of  some  of  the  lower  vegetable  organisms  as  certain  molds, 
yeasts,  and  bacteria,  also  many  of  the  enzyms  which 
show  selective  action  in  destroying  one  antipode.  Fischer 
showed  that  the  yeasts,  as  a  rule,  attacked  the  naturally 
occurring  dextrorotatory  forms  of  dextrose,  maltose,  and 
mannose,  but  did  not  ferment  the  levo-isomers  separated 
by  synthetic  processes.  On  the  contrary,  levulose  was 
attacked,  but  not  its  dextro-isomer. 

Determinations  of  Specific  Rotatory  Power.  —  In  the  ex- 
planation of  specific  rotatory  power,  previously  given,  only 
an  allusion  was  made  to  the  disturbing  effects  of  solvents 
and  temperature  which  occur  in  the  case  of  many  com- 
pounds, as  these  influences  on  the  sugars  heretofore 
discussed  are  so  slight  as  to  be  of  little  importance  in 
most  commercial  analysis.  Invert  sugar  and  the  tempera- 
ture influence  on  milk  sugar  are  excepted,  temperature 
coefficients  of  which  have  been  given. 

Since  the  specific  rotations  of  the  ray  of  standard  wave 
length  caused  by  many  substances,  when  calculated  from 
solutions  of  different  concentrations  and  from  those  in 
different  solvents,  do  not  give  constants,  it  is  customary 
in  practical  work  to  calculate  such  values  from  solutions 
made  from  the  specified  solvent  containing  10  grams  of 
substance  in  100  cubic  centimeters  (or  what  is  usually 

1  Ber.  d.  ckem.  Ges.,  23,  370,  799,  2133;  25»  I255- 


THE  POLARISCOPE   IN   SCIENTIFIC   RESEARCH          245 

sufficiently  identical  for  this  purpose,  a  concentration  of 
10  per  cent),  readings  being  taken  at  20°  to  eliminate  any 
temperature  disturbance. 

To  eliminate  the  influence  of  the  solvent,  the  so-called 
"  absolute "  specific  rotation  of  an  optically  active  sub- 
stance is  often  calculated.  Biot,  in  investigations  begun  in 
^838,  and  extending  over  twenty  years,  showed  that  this 
could  be  obtained  by  plotting  curves  representing  the 
variations  in  the  apparent  specific  rotation  calculated  from 
different  concentrations  of  solution,  each  solvent  giving  an 
independent  curve.  If  the  per  cent  of  solvent  in  each 
solution  polarized  is  plotted  as  an  abscissa,  and  the  corre- 
sponding value  of  the  apparent  specific  rotation  as  an  ordi- 
nate,  a  curve  is  made  which  is  either  a  straight  line  or  can  be 
considered  a  hyperbola  or  parabola.  If  the  line  is  straight, 
the  absolute  specific  rotatory  power  can  be  expressed  by 
the  formula  a  =  A  -f  Bq,  where  q  is  the  per  cent  of  sol- 
vent present,  and  the  constants  A  and  B  calculated  from 
the  plots,  A  being  the  absolute  specific  rotation,  B  the  rate 
of  its  change  with  the  quantity  of  solvent  present.  If 
the  line  is  a  curve,  the  equation  [a]/>  =  A  +  Bq  +  Cq2  is 
sufficiently  correct  for  practical  purposes  in  the  majority 
of  cases.  If  the  per  cent  of  active  substance  is  expressed 
by  p,  the  equations  become  [a]/)  =  A  +  B(ioo  —  /)  and 
[IL]D  =  A  +  £(ioo  —  /)+  C(ioo—  /)2.1 

In  the  equation  [a]jD  =  A  +  Bq  +  Cq*,  the  constants  B 
and  £7  can  be  obtained  by  determining  the  apparent  specific 
rotations  from  three  solutions  of  different  concentrations  : 

1  So,  too, pd can  be  substituted  for/,  giving  the  equation  for  concentration 
expressed  as  —  •  As  the  density  influence  of  most  substances  in  solution  is 
not  a  constant,  however,  such  equations  are  not  precise. 


246         THE  POLARISCOPE   IN   SCIENTIFIC   RESEARCH 

[a]  n  =  A  +  B9l+  Cqf.  (I) 

[*\H  =  *  +  Bq*+ Cqf.  (2) 

[aU^  +  .ffft+Cft*  (3) 

If  (2)  is  subtracted  from  (i)  and  (3)  from  (2) : 

l>]  BI  -  M  »2  =  *(ft  -  ft)  +  C(fta  -  ?22>  (4) 

[ata  -  |VU  =  B(qt  -  ft)  +  C(<722  -  ft*).  (5) 

From  (4)  B  =  M*"  M** 

ft- ft 


ft-ft 

From  (5)  B  =  M^-IXU  _  ^  +  ^ 

Hence :  C=  ,  Mi"  E<U«    _    I>L*  ~  M* 


Landolt  has  proved  by  experiment,  in  the  case  of  a  large 
number  of  optically  active  substances,  that  the  value  A, 
determined  mathematically  by  Biot's  formulae,  represents 
the  true  or  absolute  specific  rotation. 

The  example  most  cited  is  that  of  oil  of  turpentine.  If 
the  specific  rotation  of  this  substance  is  determined  directly 
by  polarizing  the  pure  oil,  free  from  solvent,  the  specific 

rotation,  calculated  from  the  formula  a  =  y^  is  14.15°.     If 

Let 

the  specific  rotation  values  are  obtained  from  alcoholic 
solutions  of  various  concentrations,  the  values  increase 
with  the  dilution,  an  80  per  cent  solution  having  a  specific 
rotation  of  about  14.4°,  a  20  per  cent  about  15.2°.  The 
plotted  values  obtained  at  different  concentrations  form  a 


THE   POLARISCOPE   IN   SCIENTIFIC   RESEARCH         247 

straight  line,  which  is  represented  by  the  equation  [a]/>  = 
14. 17 +  .00178  q,  A  in  this  case  being  identical  within 
experimental  error  with  the  value  actually  obtained  by 
polarizing  the  pure  oil,  free  from  solvent. 

In  cases  where  it  is  impossible  to  polarize  the  substance 
free  from  solvent,  as  in  the  case  of  camphor  or  tartaric 
acid,  plots  made  by  dissolving  the  substances  in  different 
solvents  give  curves  which,  while  of  different  forms,  all 
converge  to  a  common  focus,  which  expresses  the  com- 
mon value  of  A  obtained  in  each  equation.  In  some  cases 
these  curves  show  an  increase  in  apparent  value  of  the 
specific  rotation  with  dilution,  as  in  the  case  of  oil  of  tur- 
pentine and  tartaric  acid ;  in  others  a  decrease,  as  those  of 
camphor  and  tartaric  acid.  Nicotine  in  dilute  water  solu- 
tions is  peculiar  in  giving  a  curve  which  gradually  decreases 
with  dilution  to  a  minimum  at  about  8  per  cent,  and  then 
increases.  Camphor  shows  the  same  minimum  value  with 
some  solvents.  Malic  acid  and  its  sodium  salts  show 
even  a  reversal  of  the  direction  of  rotation  at  certain 
concentrations.1 

The  temperature  effects  on  the  specific  rotations  of 
optically  active  solutions  have  not  been  formulated  except 
in  comparatively  few  instances. 

The  rotation  of  a  mixture  of  optically  active  substances 
in  solution,  when  these  substances  do  not  react  upon  each 
other,  is  the  resultant  of  their  individual  rotatory  effects, 
as  has  been  proved  by  many  experiments.  Acids,  alkalies, 
and  many  salts  influence  the  rotatory  effects  of  optically 

1  See  Landolt's  "  Optische  Drehungsvermogen  "  for  a  complete  account  of 
the  researches  on  specific  rotation.  See  also,  on  tartrates,  E.  B.  and  F.  B. 
Kenrick,  /.  Am.  Chem.  Soc.,  26,  665. 


248         THE   POLAR1SCOPE   IN   SCIENTIFIC   RESEARCH 

active  bodies,  but  in  most  cases  present  knowledge  is 
insufficient  to  show  whether  in  certain  cases  chemical 
action  takes  place  or  not.  Apparently  in  some  cases 
polymerization  affects  optical  rotation,  although  many 
experiments,  as  those  with  itaconic  acid,1  show  the 
opposite. 

A  large  and  attractive  field  of  research  in  physical  chem 
istry  is  opened  and  yet  but  little  worked  in  optical  investiga- 
tions of  molecular  structure  by  means  of  the  polariscope. 
The  only  line  which  has  been  followed  up  in  this  direction 
to  any  extent  has  been  that  pointed  out  by  the  researches 
of  Pasteur  and  Van't  Hoff. 

Attempts  have  been  made  to  apply  the  theory  of  elec- 
trolytic dissociation  to  optically  active  solutions  containing 
salts,  acids,  and  bases  ;  and  the  investigations  of  Oudemans 
and  later  Hadrich2  on  alkaloids  have  established  the  fol- 
lowing law :  the  rotating  power  of  electrolytes  in  general 
in  dilute  solutions,  where  the  dissolved  substance  is  largely 
dissociated  into  its  ions,  is  independent  of  the  inactive 
constituents  of  the  salt.  For  instance,  different  quinidine 
salts  diluted  to  the  extent  of  a  "gram  equivalent"  (the 
molecular  weight  in  grams)  in  20  liters  of  water  or  more, 
show  identical  rotation  values  which  gradually  increase 
up  to  a  dilution  of  the  gram  equivalent  in  80  liters 
being  constant  at  greater  dilutions.  The  salts  of  mor 
phine  behave  in  a  similar  way,  as  do  those  of  brucine 
and  strychnine,  although  the  specific  rotation  becomes 
constant  in  the  case  of  the  two  latter  alkaloids  at  lower 
dilutions. 

1  Walden,  Zeit.phys.  Chem.,  20,  383. 

2  Hadrich,  Ann.  Chem.  Liebig,  207,  257. 


THE   POLARISCOPE   IN    SCIENTIFIC   RESEARCH         249 

Molecular  Specific  Rotation.  —  In  calculations  of  the  rota- 
tory effect  of  the  molecule  in  physical  chemistry,  the 
"molecular  rotation"  (symbolized,  M)  is  sometimes  used 
as  the  optical  unit.  This  is  obtained  by  multiplying  abso- 
lute specific  rotation  by  the  molecular  weight  of  the  sub- 
stance. Usually  for  convenience  T^  of  this  unit  is  taken 
(symbol,  [M~]). 

Many  attempts  have  been  made  to  establish  laws  which 
would  express  the  influence  of  molecular  structure  on  rota- 
tion values,  but  with  little  success,  the  Van't  Hoff-Le  Bel 
theory  being  still  incomplete  on  these  lines,  as  shown  by 
the  work  of  Guye,  Walden,  and  others.  The  principal  law 
which  does  hold  good  is  one  of  Van't  Hoff  that  if  a  com- 
pound contains  several  "asymmetric"  carbon  atoms  and 
consequently  several  optically  active  groups,  the  rotation  is 
the  algebraic  sum  of  the  group  rotations.  This  has  been 
found  to  be  exactly  true  by  the  work  of  Guye l  and  Walden 
on  the  liquid  amyl  esters,  and  is  of  vital  importance,  as  on 
its  establishment  depends  the  correctness  of  the  whole 
theory  of  isomeric  sugars  as  developed  by  Fischer,  as  well 
as  the  methods  of  investigation  of  hydrolyzed  starch  com- 
pounds already  explained. 

Multirotation  ("birotation  ").  —  Many  sugars  when  freshly 
dissolved  and  polarized  give  initial  temporary  rotation 
values  which  gradually  change  and  become  constant  after 
some  hours.  This  phenomenon  was  first  observed  by 
Dubrunfaut,  in  1846,  in  dextrose  solutions.  This  transi- 
tion condition  of  the  specific  rotation  has  since  been  found 
to  exist  in  many  sugars  and  other  compounds  as  well,  as 
in  oxyacids  and  their  lactones,  nicotine,  and  some  amine 

1  Guye,  Compt.  rend^  121,  827. 


250         THE   POLARISCOPE  IN   SCIENTIFIC   RESEARCH 

bodies.  The  optical  values  may  increase  or  decrease 
toward  a  constant,  and  some  sugars  form  two  optically 
unstable  or  "  labile  "  modifications,  according  to  the  condi- 
tions of  their  extraction  from  concentrated  solutions.  Both 
these  forms  revert  to  the  stable  condition  at  a  rate  depend- 
ent on  the  presence  of  any  catalytic  bodies  which  hasten 
the  change ;  the  laws  of  the  rate  of  hydrolytic  change  of 
Wilhelmy  and  the  principle  that  the  influence  of  the  acids 
was  proportional  to  their  "  affinity  constants "  applying 
generally.  Alkalies,  even  in  very  dilute  solutions  (.1  per 
cent  ammonia,  for  instance),  produce  an  almost  immediate 
change  of  rotation  to  the  constant  value,  and  by  prolonged 
action  at  greater  concentrations  produce  changes  in  ro- 
tations of  many  of  the  sugars  which  can  only  be  explained 
by  the  formation  of  new  compounds.  Lobry  de  Bruyn 
and  Van  Ekenstein  have  shown  that  this  is  due  to  the 
formation  of  isomeric  sugars  rather  than  phenomena  of 
multirotation. 

Bringing  the  optically  active  solution  to  a  boil  gives  the 
constant  rotation  value,  for  the  optical  transition,  analogous 
to  hydrolytic  change,  is  enormously  accelerated  by  tempera- 
ture increase.  As  already  noted,  this  latter  procedure  of 
heating  the  solution  is  necessary  in  analytical  operations, 
as,  for  instance,  when  dealing  with  freshly  dissolved  milk 
sugar  or  dextrose.  Cane  sugar  shows  no  multirotation. 
The  monohydrate  of  dextrose,  which  is  the  form  which 
commercial  "  grape  sugar  "  takes,  shows  multirotation  simi- 
lar to  the  anhydride. 

The  following  table  shows  the  specific  rotations  of 
the  labile  and  stable  forms  of  the  more  important 
sugars : 


THE   POLARISCOPE   IN   SCIENTIFIC   RESEARCH         251 


Dextrose.     .     .     .  52.7°  105.2°         22.5° 

Galactose      .     .     .  81.6°  135.0°         52.3° 

Lactose    ....  52.5°  86.2°         34.4° 

Maltose    ....  138.0°  118.2° 

Levulose       ...  -  92.5°      -  104.0° 

Arabinose1  .     .     .  104.4°  156.7° 

Xylose1   ....  19.2°  94-4° 


a  is  the  labile  solution  made  by  dissolving  the  crystallized 
sugar  in  water  ;  (3  the  stable  solution  ;  -y  a  second  unstable 
form,  usually  produced  by  heating  the  residue  evaporated 
from  solution,  or  by  precipitation  with  alcohol. 

Multirotation  seems  to  be  a  phenomenon  resulting  from 
hydration  of  the  substance,  accompanied  by  a  rearrange- 
ment of  the  optically  active  groups,  but  it  has  not  been 
completely  explained. 

Laws  of  Hydrolytic  Change.  —  The  polariscope  has  been 
of  great  service  to  science  as  a  means  of  measurement  of 
comparative  chemical  activity  of  hydrolyzing  substances, 
particularly  acids  ;  and,  as  the  constants  so  obtained  have 
a  very  direct  and  intimate  relation  to  those  determined  by 
electrical  conductivity  and  other  methods  of  measurement 
of  chemical  affinity,  they  are  usually  termed  "  affinity  con- 
stants." 

Wilhelmy,  in  1850,  was  the  first  to  formulate  a  mathe- 
matical expression  of  the  laws  governing  the  chemical 
change  produced  by  hydrolysis.  Thereby  was  opened  up 
a  field  of  research  which  has  had  enormous  influence  on 
the  science  of  chemistry  as  a  whole,  and  greatly  widened 

1  Pentose  sugars  (C5H10O5). 


252         THE   POLARISCOPE   IN   SCIENTIFIC   RESEARCH 

our  comprehension  of  the  mechanism  of  chemical  action. 
His  formulation  is  as  follows :  If  B  is  the  original  amount 
of  sugar  subjected  to  inversion  at  a  fixed  temperature  under 
the  influence  of  an  acid  of  known  concentration  A,  and  dx  is 
the  amount  inverted  in  a  given  increment  of  time  dt ;  x  will 
represent  the  sugar  inverted  at  the  end  of  t  minutes,  and 

dx 

—  =  cA(B  —  x\  where  c  is  a  constant  dependent  on  the 

nature  of  the  acid  and  temperature. 

By  the  mathematical  method  of  integration,  this  becomes: 

r> 

nat  log -  =  Act. 

B  —  x 

B,  the  amount  of  cane  sugar  at  the  start  (or  at  any  chosen 
moment  during  the  reaction  when  t  is  taken  as  zero),  is 
directly  proportional  to  R  —  R1 ',  where  R  is  the  reading  of 
the  polariscope  given  by  the  sugar  solution  at  this  chosen 
moment,  Rf  the  reading  of  the  solution  when  completely 
inverted.  The  value  of  B  —  x  is  proportional  to  R"  —  Rf, 
Rf[  being  the  polariscope  reading  taken  at  the  time  t. 
Evidently  Ac  is  a  constant  as  calculated  from  this  equa- 
tion, since  the  concentration  of  the  acid  remains  unchanged 
throughout  the  inversion,  owing  to  its  action  being  catalytic. 

If  a  series  of  the  constants  are  obtained  from  inverting  a 
sugar  solution  by  different  acids,  under  fixed  conditions  of 
temperature  and  concentration,  their  ratios  will  represent 
the  comparative  affinities  of  the  two  acids.  Usually  these 
are  expressed  in  terms  of  the  affinity  value  of  hydrochloric 
acid  taken  as  100. 

The  method  of  determining  these  afrinity  constants  does 
not  require  detailed  description.  Outside  of  the  usual 
precautions  necessary  in  precise  polarimetric  observations, 


THE   POLARISCOPE   IN   SCIENTIFIC   RESEARCH         253 

the  influence  of  even  minute  temperature  variation  must 
be  guarded  against  with  particular  care.  The  polariscope 
tube  or  bath  in  which  the  inversion  is  taking  place  must 
be  carefully  protected  from  radiation,  and  be  kept  at  a 
constant  temperature  by  means  of  a  circulating  jacket  or 
other  similar  device  in  which  the  water  temperature  is  kept 
constant  within  the  limits  of  measurement  of  a  delicate 
thermometer,  certainly  within  .01°  for  accurate  work. 
Ingenious  thermostats  have  been  specially  devised  for  this 
accurate  control. 

Polarimetric  readings  are  made  at  regular  time  intervals 
reckoned  in  minutes  from  any  chosen  period  in  the  course 
of  the  inversion  taken  as  an  initial  point.  The  reading  of 
the  solution  when  so  completely  inverted  that  no  further 
change  in  the  readings  occurs  must  also  be  known. 

As  the  value  of  the  ordinary,  or  Briggs,  logarithms  bears 

a  constant  relation  f—     -  j  to  those  of  the  "natural"  or 

V-4343; 

Naperian  logarithms,  the  former  are  usually  more  conven- 
ient to  use,  as  the  constant  values  so  obtained  can  be 
readily  converted  into  the  true  constants  as  derived  from 
the  exact  formula.  The  calculation  is  very  simple,  as  the 
equation  given  above  shows.  The  logarithm  of  the  differ- 
ence between  the  reading  of  the  solution  at  the  time  t  and 
the  reading  of  the  completely  inverted  solution  is  subtracted 
from  the  logarithm  of  the  difference  between  the  reading 
at  the  initial  moment  when  /  is  taken  as  zero  and  that  of 
the  completely  inverted  solution.  The  value  thus  obtained 
for  each  reading  is  divided  by  the  appropriate  number  of 
minutes  which  determine  the  time  of  the  reading,  the 
quotient  giving  the  required  constant. 


254         THE   POLARISCOPE   IN   SCIENTIFIC   RESEARCH 

The  influence  of  temperature  on  hydrolytic  change  is 
very  great,  the  increase  up  to  about  80°  causing  a  very  rapid 
acceleration  in  the  rate  of  inversion.  Above  this  tempera- 
ture, the  temperature  coefficient  gradually  diminishes, 
the  plot  of  the  values  forming  a  convex  parabolic  curve. 
Unfortunately  for  the  practical  applications  of  the  laws  of 
hydrolytic  change,  in  spite  of  the  enormous  mass  of  data 
which  have  been  collected,  these  temperature  coefficients 
under  different  conditions  of  inversion  have  not  been  for- 
mulated into  any  law  of  general  application. 

The  work  of  Spohr,  Urech,  and  Arrhenius  has,  however, 
developed  the  following  equation  to  express  change  in  the 
inversion  constant  of  an  acid  at  any  temperature  /0  be- 
tween  I   and  50°  :  A^-TJ 
C^CfC-sZT, 

T0  being  the  temperature  at  which  the  inversion  is  made 
and  7^  that  at  which  the  other  inversion  takes  place,  both 
being  expressed  in  absolute  temperatures  (/+ 273°).  e  is 
the  natural  logarithmic  base,  2.718281.  As  this  equation 
requires  the  determination  of  a  new  constant,  apparently 
dependent  on  the  special  conditions  of  the  inversion,  it 
can  be  applied  only  in  specific  cases  where  such  constants 
have  been  determined  with  more  or  less  accuracy. 

Sigmond  found  the  value  of  A  to  be  12820  at  69.3°  C,  or 
at  about  the  most  favorable  inverting  temperature  of  sucrose 
He  also  found  the  equation  held  to  100°  (Zeit.  Phys.  Chem., 
27,  386). 

Until  these  temperature  laws  on  the  constants  of  inver- 
sion for  the  common  acids  are  developed  more  completely, 
the  results  of  modern  physical  chemical  research  on  hydro- 
lytic change  will  have  but  a  limited  practical  application 


THE   POLARISCOPE   IN   SCIENTIFIC   RESEARCH         2$ 5 

for  the  sugar  chemist,  but  they  promise  much  in  the  future. 
This  sketch  of  the  more  important  laws  bearing  on  the 
subject  is  introduced  here  merely  to  point  out  the  great 
value  of  polarimetric  investigations  in  this  line. 

Hydrolysis  of  Starch.  —  In  the  hydrolysis  of  starch  prod- 
ucts, the  law  expressing  the  rate  of  change  is  obviously 
more  complicated;  for,  if  we  consider  the  hydrolysis  as 
practically  the  resolution  of  the  primary  dextrin  groups 
into  maltose  and  the  simultaneous  inversion  of  the  latter 
into  dextrose,  evidently  the  reaction  has  to  deal  with  two 
distinct  chemical  transformations  taking  place  at  the  same 
time.  The  transformation  of  dextrin  into  maltose  is  in 
accord  with  the  law  discussed  above,  and  consequently 
can  be  expressed  as  in  sucrose  inversion  by  the  equation : 

(i) 


A  formula  can  be  derived  from  the  exact  differential  equa- 
tion,1 -  —  =  c^M,  which  states  that  the  amount  of  dextrose 
at 

(Z>)  formed  at  each  moment  is  proportional  to  the  amount 
of  maltose  (M}  present  by  replacing  the  differential  quan- 
tities by  finite  differences  which  in  applications  of  the  for- 
mulae must  be  taken  small.  In  the  place  of  M,  the  average 
amount  of  maltose  present  during  the  interval  of  time  con- 
sidered is  substituted.  That  is,  if  M^  and  M^  are  the 
amounts  of  maltose  present  at  these  times,  and  c2  is  the 
reaction  constant,  the  result  of  the  above  substitution  is : 

=  '*  (2) 


/,  - 


1  Tech.  Quart.,  1897,  T55  (revised  froih/.  Am.  Chem.  Soc.,  1896,  18). 


256         THE   POLARISCOPE   IN   SCIENTIFIC   RESEARCH 

By  these  formulae  two  constants  were  found  for  each 
conversion  in  a  series  of  hydrolyses  of  corn  starch  made 
with  different  acids  under  varying  conditions  of  concentra- 
tion of  the  hydrolyte  and  temperature.  As  the  hydrolysis 
of  starch  is  relatively  slow  with  dilute  acids  at  ordinary 
laboratory  temperatures,  the  reactions  were  carried  out 
under  steam  pressure  varying  from  i  to  4  atmospheres  in 


FIG.   38.  —  DIAGRAM  OF  AUTOCLAVE   FOR  ACID    HYDROLYSIS  OF   STARCH 
ARRANGED  FOR  REMOVAL  OF  SAMPLES  WITHOUT  INTERRUPTION. 

an  autoclave  specially  arranged  for  removal  of  portions  of 
the  solution  at  any  desired  stage  of  the  hydrolysis.  The 
amounts  of  dextrin  and  maltose  per  unit  of  total  carbohy- 
drate in  solution  were  calculated  from  the  specific  rotatory 
power  of  the  solutions,  by  the  method  described  in  a  pre- 
vious chapter.  The  values  so  obtained  were  fairly  constant, 
tending  to  increase  slowly  as  the  hydrolysis  proceeded. 


THE   POLARISCOPE  IN   SCIENTIFIC   RESEARCH         257 

The  comparative  affinity  constants  of  the  acids  used  (hy- 
drochloric, acetic,  sulphuric,  oxalic,  and  sulphurous)  derived 
from  the  results  of  this  investigation,  gave  values  in  practi- 
cal agreement  with  those  obtained  from  sugar  inversion.1 

Application  of  the  Quartz-wedge  Saccharimeter  to  General 
Polarimetric  Measurements.  —  The  great  convenience  in 
manipulation  and  the  precision  of  the  quartz-wedge  sac- 
charimeter make  it  the  most  desirable  instrument  for 
polarimetric  measurements  when  its  use  is  permissible. 
The  application  of  the  quartz-wedge  saccharimeter,  how- 
ever, is  strictly  limited  by  the  following  conditions  :  (i)  the 
restricted  scale  which  measures  rotations  between  about 
35°  and  —  10°,  although  these  measurements  can  be  ex- 
tended by  the  use  of  standard  quartz  plates  of  known 
dextro-  and  levorotatory  values ;  (2)  the  necessary  condition 
that  the  " rotatory  dispersion"  of  the  solutions  polarized 
closely  approximates  to  that  of  quartz ;  that  is,  if  the  ratios 
of  the  rotations  of  the  different  rays  of  the  spectrum 
caused  by  the  solution  are  not  practically  identical  with 
those  given  by  quartz,  there  will  be  no  position  of  the 
wedges  at  which  the  proper  thickness  of  quartz  can  be 
interposed  to  give  complete  compensation.  Consequently, 
in  such  cases,  the  end  point  given  by  the  solution  will  not 
be  identical  with  that  at  the  zero  reading,  and  the  precision 
of  the  measurement  will  be  seriously  impaired  thereby. 
In  the  standard  shadow  saccharimeter,  this  unequal  dis- 
persion manifests  itself  by  a  party-colored  field  at  the  end 
point  instead  of  an  equally  tinted  one.  As  the  rays  at  the 
violet  end  of  the  spectrum  are  the  principal  disturbing 

1  For  speed  of  hydrolysis  of  starch  by  diastase.  See  Brown  and  Glendin- 
ning,/.  Chan.  Soc.,  81,  388. 


258          THE   POLARISCOPE   IN   SCIENTIFIC   RESEARCH 

ones,  this  party-colored  field  can  be  largely  prevented  by 
filtering  the  light  through  a  solution  of  potassium  bichro- 
mate, or  a  section  of  a  crystal  of  this  substance,  when 
the  difference  in  dispersion  is  not  great.  In  the  case  of 
commercial  glucose  and  most  starch  products,  as  well  as 
sugars  other  than  sucrose,  the  bichromate  cell  is  effectual, 
md  is  usually  part  of  the  equipment  of  the  saccharimeter. 
If  the  inequality  of  dispersion  is  considerable,  as  in  the 
case  of  many  essential  oils,  sodium  light  must  be  used. 

Light  Factor.  —  The  equivalent  of  one  division  of  the 
saccharimeter  in  angular  degrees  of  rotation  of  the  plane 
of  polarization  of  the  standard  yellow  ray  is  called  the 
"  light  factor  "  of  the  saccharimeter.  Until  comparatively 
recently,  the  factor  .3455  was  considered  correct1  in  all 
cases  to  convert  readings  in  divisions  of  the  Ventzke  scale 
to  rotations  of  standard  yellow  light  in  angular  degrees. 
Landolt  in  1888  and  Rimbach  in  1894  published  results 
of  comparative  readings  of  various  sugars,  showing  that 
this  factor  varied  in  many  cases  with  the  nature  of  the 
sugar,  being  nearer  to  .345  for  dextrose,  for  instance,  than 
.346;  and  establishing  the  fact  that  the  light  factor  is 
not  a  constant,  but  varies  with  the  nature  of  the  solution 
polarized,  being  dependent  on  the  difference  between  the 
dispersion  of  the  substance  and  that  of  quartz,  as  it  is, 
obviously,  on  temperature.  There  are  also  other  variations 
in  light-factor  values  which  have  caused  considerable  con- 
fusion in  establishing  the  exact  equivalent  of  the  standard 
quartz-wedge  saccharimeter.  These  are  due  to  the  fact  of 
the  existence  of  saccharimeters  with  scales  based  on  a  dif- 

1  This  factor  is  correct  for  the  rotation  equivalent  as  determined  by  quartz 
readings  on  the  Laurent  polariscope  at  17.5°. 


THE   POLARISCOPE   IN   SCIENTIFIC   RESEARCH         259 

ferent  graduation  from  that  of  the  Ventzke  standard,  and 
furthermore  to  changes  in  the  optical  centre  of  the  yel- 
low light  used  as  the  standard  of  measurement  in  rotatory 
polariscopes.  The  factor  .3458  is  correct  at  20°  for  con- 
version of  the  divisions  of  the  standard  Ventzke  scale  into 
angular  degrees  of  rotation  as  given  on  the  Laurent  sac- 
charimeter,  for  substances  having  the  same  dispersive 
power  as  quart z^  If,  however,  the  light  standard  of  the 
Lippich  ray  filter  is  taken,  the  light  factor  becomes  .3466, 
while  with  the  true  centimeter  saccharimeter  scale,  the 
factor  is  more  nearly  .3469.  In  the  case  of  cane  sugar,  the 
factor  is  practically  the  same  as  quartz  under  the  same 
standards  of  measurement,  but  with  hydrolyzed  starch 
products,  with  the  Ventzke  saccharimeter,  it  varies  from 
.3443  for  the  Laurent  standard  at  20°  to  about  .3450  with 
the  Lippich  ray.  If  sodium  light  is  used  with  the  saccha- 
rimeter, the  influence  of  dispersion  will  be  eliminated,  and 
the  factor  will  be  constant  at  the  same  temperature  for 
all  solutions.  Use  of  sodium  light  sacrifices  much  of  the 
convenience  of  the  quartz-wedge  saccharimeter,  but  quali- 
fies the  instrument  for  measurements  of  all  optically  active 
substances.2 

1  Throughout  this  book,  it  has  been  assumed  on  the  authority  of  Landolt 
(p.  364)  that  sodium  light  passed  through  the  Lippich  ray  filter  has  an  optical 
centre  practically  identical  with  that  of  the  spectrally  purified  light  (see  foot- 
note, p.  n).     Recent  rotation  measurements  of  quartz  plates  do  not,  however, 
confirm  this  identity  in  every  case. 

2  If  the  modern  quartz-wedge  saccharimeter  is  graduated  to  give  the  exact 
sugar  values  for  solutions  at  all  concentrations  represented  on  the  scale,  as 
Von  Lippmann  ("Chem.  der  Zuckart.,"  Ill  ed.  1363)  asserts  and  many  of  the 
quartz-plate  readings  made  by  the  author  show,  obviously  the  light  factor  in 
the  middle   of  the  scale  will  be   slightly  different   from   that   at  the  ends. 
For  instance,  the  light  factor  of  a  U.  S.   standard  instrument  apparently  so 
graduated  is  .3467  at  the  100  point,  but  .3469  at  the  60. 


APPLICATION  OF  THE  POLARISCOPE  TO 
CHEMICAL  ANALYSIS  OTHER  THAN  CAR- 
BOHYDRATE DETERMINATIONS 

WHILE  there  is  a  wide  field  for  the  application  of  the 
polariscope  in  the  analysis  of  many  organic  compounds, 
comparatively  few  systematic  methods  of  analysis  have 
been  developed  as  yet.  Perhaps  one  reason  for  this  neg- 
lect of  the  polariscope  in  quantitative  organic  analysis  is 
due  to  the  fact  that  the  specific  rotations  of  most  optically 
active  substances  are  affected  to  a  large  extent  by  the  sol- 
vents usually  necessary  in  polarizing,  as  explained  in  the 
preceding  chapter.  In  consequence,  since  in  the  simple 
equation  expressing  the  fundamental  laws  of  rotation, 

a  =  -  — ,  a  is  not  a  constant  at  different  concentrations,  as 

v 

it  is  practically  in  the  case  of  cane  sugar,  the  formula  for 
calculation  of  the  optically  active  substance  is  often  very 
complicated.  This  drawback  is  not  a  serious  one,  how- 
ever, as  is  shown  by  the  steadily  increasing  number  of 
polarimetric  methods  which  are  being  applied  in  organic 
analysis,  and  these  will  become  of  more  general  use  as  the 
fundamental  principles  of  optical  analysis  become  better 
known.  As  will  be  explained  farther  on,  another  reason 
why  little  has  been  done  in  applying  polarimetric  methods 
to  the  quantitative  measurement  of  the  optically  active 
substances  themselves  is  the  variation  of  these  constituents 
in  most  plant  products,  such  as  the  essential  oils  and 

260 


MISCELLANEOUS   APPLICATIONS  26 1 

drugs,  as  well  as  the  complication  of  their  mixture. 
Hence  the  polariscope  has  been  of  service  principally  in 
determining  the  purity  of  such  products  as  are  character- 
ized by  approximate  rotation  constants.  These  rotation 
figures  in  conjunction  with  the  density  and  refractive  index 
have  been  particularly  valuable  in  the  identification  of  the 
essential  oils  and  detection  of  adulterants.  The  indica- 
tions of  the  instrument  in  such  cases  can  be  looked  on  as 
in  a  sense  qualitative  rather  than  quantitative. 

In  general,  the  rotatory  polariscope  is  more  suitable  for 
determinations  of  oils  and  drugs,  owing  to  the  great  varia- 
tion in  the  rotation  dispersion  of  these  substances.  The 
quartz-wedge  saccharimeter  is,  however,  universally  appli- 
cable if  sodium  light  is  used  as  the  illuminant  and  the 
readings  are  converted  into  angular  rotation  equivalents 
by  the  appropriate  light  factor.  As  many  of  the  liquid 
products  can  be  put  into  the  polariscope  tube  without 
preparation  and  polarized  directly,  and  as  the  specific  ro- 
tations are  often  very  large,  it  may  *be  advisable  to  use 
tubes  of  shorter  lengths  than  for  sugar  analysis,  even  as 
short  as  .25  decimeter.  In  exact  quantitative  measure- 
ments with  such  tubes,  due  allowance  must  be  made  for 
the  increased  error  in  the  use  of  such  short  lengths. 

Camphor.  —  Forster 1  has  devised  a  method  for  deter- 
mining camphor  in  celluloid  which  is  as  follows :  About 
10  grams  of  celluloid  are  saponified  with  four  times  this 
weight  of  sodium  hydrate  (10  per  cent).  After  dilution 
with  water,  the  camphor  is  distilled  off  with  steam  and  col- 
lected in  about  25  cubic  centimeters  of  benzol  by  shaking 

1  Ber.  deut.  chem.  Ges.,  23,  2981.  See  also  for  camphor  in  oils,  Leonard 
and  Smith,  Analyst,  25,  202. 


262  MISCELLANEOUS   APPLICATIONS 

up  the  distillate  with  that  liquid.  After  making  up  to  a 
definite  volume,  the  benzol  solution  is  polarized  at  20°  C. 
The  specific  rotation  is  expressed  by  the  following 
formula,  [a]£2o=  39.755  4- .1725  w,  from  which  is  derived 

s    \  2 

2^=2.4683  - — .01747  f-  j   for  the  weight  of  camphor  in 
/  \/  / 

100  cubic  centimeters.  The  equation  is  more  complicated 
than  that  expressing  the  concentration  of  sugar  solutions, 
owing  to  the  marked  action  of  the  solvent  on  the  rotation.1 

Chinchona  Alkaloids.  —  The  valuable  medicinal  alkaloids 
of  the  chinchona  plants  are  very  numerous,  over  thirty 
having  been  isolated.  They  are  all  tertiary  amines, 
strongly  basic  in  their  nature,  and  most  of  them  of  pro- 
nounced optical  activity.  Isomers  and  polymers  are  often 
found  together,  so  that  an  exact  determination  of  the  con- 
stituent alkaloids  in  the  bark  of  the  plant  by  any  polari- 
metric  method  is  too  complicated  to  be  practical.  An 
additional  difficulty  is  the  great  influence  that  the  ordinary 
solvents  of  these  alkaloids  have  on  their  specific  rotations. 

It  is  usually  necessary  to  isolate  the  alkaloids  by  chemi- 
cal separation  processes  before  making  a  quantitative 
determination  by  the  polariscope.  Many  such  processes 
are  in  use.  One  will  illustrate,  —  the  determination  of 
quinine  and  chinchonidine  in  a  chinchona  bark : 

All  the  alkaloids  present  are  first  set  free  by  treating 
the  powdered  bark  with  calcium  hydrate,  by  making  a 
paste  with  water ;  then  extracting  with  a  mixture  of  three 
parts  of  benzol  and  one  of  amyl  alcohol,  by  boiling  for 
half  an  hour,  and  filtering  off  from  the  residue ;  and  finally 
removed  as  the  hydrochlorates,  by  treatment  with  dilute 

1  Landolt,  "  Optische  Drehungsvermogen,"  169,  also  453. 


MISCELLANEOUS  APPLICATIONS  263 

hydrochloric  acid  in  a  separatory  funnel.  The  acid  solu- 
tion is  carefully  neutralized  with  ammonia,  and  the  quinine 
and  chinchonidine  precipitated  as  tartrates  with  Rochelle 
salt. 

The  precipitation,  which  is  facilitated  by  stirring,  is  com- 
pleted in  about  an  hour.  Eighty  per  cent  of  the  weight 
of  the  washed  and  dried  precipitate  is  composed  of  the 
chinchonidine  and  quinine.  A  solution  convenient  for 
polarizing  can  be  obtained  by  dissolving  the  tartrates  in 
either  dilute  hydrochloric  or  sulphuric  acid.  As  the  rota- 
tion of  the  two  optically  active  substances  in  solution  l  is 
the  sum  of  their  individual  rotatory  effects,  equations  can 
be  derived  analogous  to  those  already  described  in  the 
determination  of  the  optically  active  constituents  of  hydro- 
lyzed  starch  products. 

If  x  is  the  per  cent  of  quinine  to  be  determined  in  a 
known  amount  of  the  alkaloid  salts  and  y  the  per  cent  of 
chinchonidine,  and  [a]^  is  the  specific  rotation  of  quinine 
under  the  conditions  of  solvent  and  concentration  used  in 
the  analysis,  [a]y  being  the  corresponding  specific  rotation 
of  chinchonidine  under  like  conditions : 

then,  x+y=.  100, 

and  [a]*  •  x  +  [a]y  -y  =  a 

(a  being  the  specific  rotation  of  the  alkaloid  mixture).2 
By  substituting  100  —  x  for  j,  Hesse3  develops  the  foi 

1  Correction  can  be  made  for  the  tartaric  acid  set  free  in  solution,  if  calcu- 
lation shows  that  the  error  is  large  enough  to  affect  the  results  ([a]/)  =  1.950 
+  .13030?). 

2  The  percentage  is  expressed  as  a  whole  number,  and  not  decimally  as  in 
the  equations  for  starch  hydrolysis  referred  to. 

3  Ann.  Chem.  (Liebig),  182,  146,  also  Oudemans,  ibid.,  182,  63. 


264  MISCELLANEOUS   APPLICATIONS 

lowing  form  for  the  equations  expressing  the  per  cents  of 
the  alkaloids  ; 


y=ioo        *. 
M,-  M, 

Hesse,  as  cited  by  Landolt,1  also  gives  a  modified  form  of 
these  equations  for  the  determination  of  the  mixed  alka- 
loids in  commercial  quinine  sulphate  in  which  the  rotation 
values  observed  for  a  defined  condition  of  tube-length,  sol- 
vent, and  concentration  are  substituted  for  the  specific  rota- 
tions. Two  grams  of  the  sample  are  dissolved  in  10  cubic 
centimeters  normal  hydrochloric  acid  and  the  solution 
made  with  water  to  25  cubic  centimeters,  /  being  2.2  deci- 
meters. The  angular  rotation  of  quinine  under  these  con- 
ditions is  —40.309°,  and  that  of  chinchonidine,  —26.598°. 
Hence,  for  the  conditions  defined,  if  the  corresponding 
rotation  of  the  sample  is  designated  by  Y>  the  per  cent  of 

v  +  26.598 
quinine  will  be  expressed  by  x  =  -  -  =^-,  and  the  per 

cent  of  chinchonidine  by  y  =  -  :  —  -  —  -• 

-  I37II 

Evidently  the  first  set  of  equations  is  generally  appli- 
cable, not  only  to  alkaloids,  but  to  any  two  optically  active 
substances  in  solution. 

Hesse  gives  the  following  values  for  the  specific  rotation 
of  quinine  hydrochlorate  in  water  with  varying  quantities 
of  hydrochloric  acid,  the  amount  of  acid  being  expressed 
in  "  mols  "  (the  molecular  equivalent  in  grams  in  a  liter), 

1  "  Optische  Drehungsvermogen,"  456. 


MISCELLANEOUS   APPLICATIONS  265 


the  concentration  (—  J  of  the  salt  being  2  grams  per  100 
cubic  centimeters  : 

mols  HC1          o  i  2  4  10 

[a]  ^5  --  138.75    -  223.2   -  225.7   -  223-6   -  213.9 

For  a  2-mol  solution  of  acid  and  a  concentration  of  the 
quinine  salt,  varying  between  I  and  7  grams  per  100  cubic 
centimeters,  the  following  equation  expresses  the  specific 
rotation  at  15°  C.  : 

[a]/)i5  =  —  229.46  +  2.21  w, 

or,  expressed  in  the  weight  of  the  alkaloid  : 

[a]  ^  =  —  280.78  +  3-31  w- 

The  specific  rotation  of  chinchonidine  hydrochlorate  in 
water  containing  2  mols  of  hydrochloric  acid  is  for  a  con- 
centration from  i  to  10: 

[a]/>i5=-  154-07+  1.39^- 

A  method  for  determining  the  other  alkaloids  of  chin- 
chona  bark,  in  which  polarimetric  analysis  is  used,  has 
apparently  not  been  worked  out.  The  identification  of 
any  of  the  alkaloids  after  separation,  as  well  as  determina- 
tion of  mixtures  containing  no  more  than  two,  is  obviously 
practicable  in  many  cases. 

Cocaine.  —  The  polariscope  is  said  to  be  a  valuable  aid 
in  determining  the  purity  of  this  alkaloid,  which  occa- 
sionally is  contaminated  with  dangerous  natural  impuri- 
ties, notably  cocamine.  A  polarimetric  method  of  cocaine 
determination  has  been  developed  by  Antrick,1  both  for 

1  Ber.  deut.  chem.  Ges.,  20,  320. 


266  MISCELLANEOUS   APPLICATIONS 

the  extract  and  the  hydrochlorate.  The  specific  rotation 
of  cocaine  in  chloroform  is  given  by  the  equation  [a] £20  = 
—  16.4124- .00585 /.  In  commercial  analysis  [a]/>  is  taken 
as  — 16.32.  From  this  is  derived  the  simple  equation  for 
the  per  cent  of  cocaine,  /=— 3.06— ,  where  /  is  2  deci- 
meters. 

Cocaine  hydrochlorate  has  a  specific  rotation  in  60  parts 
of  absolute  alcohol  in  90  parts  of  water,  which  is  expressed 
by  the  following  equation  : 

[a]/>2o  =  —  67.982  +  .  1 583  w. 

On  account  of  the  marked  change  in  rotation  with  varying 
amounts  of  solvent,  the  expression  for  the  per  cent  is  some- 
what complicated. 

The  simplest  expression,  which  is  given  by  Antrick,  is  : 

.7337^  +  .  001454  a2 
d 

Nicotine.  —  The  polarimetric  method  of  Popovici l  is 
used  in  conjunction  with  Kissling's  extraction  process. 
The  alkaloid  is  first  obtained  in  solution  by  treating  about 
30  grams  of  dry  pulverized  tobacco  with  10  cubic  centi- 
meters of  an  alcoholic  sodium  hydrate  solution,  made  by 
dissolving  6  grams  of  sodium  hydrate  in  100  cubic  centi- 
meters of  57  per  cent  alcohol.  The  moistened  mass  is 
extracted  for  three  hours  with  ether  in  a  Soxhlet  appa- 
ratus. The  nicotine  is  precipitated  in  an  impure  state 
from  this  ether  extract  by  adding  10  cubic  centimeters 
of  a  strong  nitric  acid  solution  of  phosphomolybdic  acid 
and  shaking  vigorously.  The  ether  is  decanted  from  the 

1  Zeilsch.  physioL  Chem.,  13,  445. 


MISCELLANEOUS  APPLICATIONS  267 

precipitate  and  water  added  to  a  volume  of  50  cubic  centi- 
meters. The  nicotine  is  finally  set  free  in  this  alkaline 
solution  by  adding  8  grams  of  dry  pulverized  barium 
hydrate.  After  standing,  with  frequent  shaking,  the  clear 
liquor  is  decanted  for  polarizing.  The  simplest  equation 

a  fa\? 

derived  by  Landolt  is,  w  —  .704-  —  .000525!  -  j  • 

Essential  Oils.  —  Most  essential  oils  are  optically  active, 
and  offer  an  attractive  field  for  polariscopic  investigations. 
As  obtained  from  plants,  these  substances  are  not,  how- 
ever, homogeneous  chemical  compounds  of  strictly  in- 
variable composition,  but  differ  considerably  with  the 
conditions  affecting  the  plant  growth  and  the  method  of 
extraction.  As  a  rule,  essential  oils  are  complicated 
combinations  of  a  large  number  of  compounds  of  very 
varied  nature. 

Among  the  more  important  well-defined  optically  act- 
ive bodies  which  have  been  isolated  from  essential  oils  are 
the  following  terpenes  of  the  general  formula,  C10H16, 
most  of  which  have  been  obtained  as  dextro-  and  levo- 
isomers  of  equal  rotating  value  : 

Pinene,  or  terebcnthene,  the  dextro-isomer  ([a]/)  =  45.04) 
being  a  characteristic  ingredient  of  American  oil  of  tur- 
pentine. The  levo-isomer  ([a]/>=  —  44.95)  is  a  compo- 
nent of  French  oil  of  turpentine. 

Camphene,  which  is  also  a  component  of  turpentine,  a 
solid  at  ordinary  temperatures,  a  levo-isomer  being  char- 
acteristic of  citronella  oil  as  well  as  of  French  turpentine. 
Camphene  is  also  a  component  of  many  other  oils,  such  as 
rosemary  and  ginger.  Its  specific  rotation,  which  seems  to 
be  about  60,  has  not  been  definitely  established. 


268  MISCELLANEOUS  APPLICATIONS 

Limonene,  whose  dextrorotatory  isomer  is  an  ingredient 
of  oils  of  orange  peel,  dill,  bergamot,  and  many  others  of 
less  importance ;  the  levorotatory  body,  being  found  in 
pine-needle  oil,  has  a  specific  rotation  of  105  at  10°  (125.6 
at  20°). 

Sylvestrene  ([a]/>=  i/.o1),  one  or  the  other  isomer  found 
in  many  turpentine  oils. 

Phellandrene(^ji\D  =  17.6),  found  in  bitter  fennel  oil.  Is 
very  unstable. 

There  are  two  important  sesqui-turpenes  (C15H24) : 

Cadinene,  found  in,  a  large  number  of  essential  oils, 
[a]/),  in  chloroform,  at  9.5°C,  for  a  13  per  cent  solution, 
=  98.56. 

Caryophyllene,  found  in  cloves  and  copaiba  balsam,  [a]/> 
=  -  8.96. 

The  following  optically  active  paraffin  alcohols  have 
been  isolated.  They  usually  are  present  in  the  oils  as 
esters  of  fatty  acids. 

Zz/ztf/<?0/(C10H17OH),  the  dextro-isomer  in  coriander  oil, 
the  levo-isomer  in  many  of  the  citrus  oils,  as  lemon,  berga- 
mot, also  in  sage,  thyme,  lavender,  spearmint,  sassafras, 
and  others.  The  specific  rotation  has  not  been  satisfacto- 
rily determined,  probably  on  account  of  impurities.  It  is 
approximately  15°. 

CiVn>«^//^/(C10H19OH),  in  dextro  form  in  rose  and  gera- 
nium oils,  has  not  had  its  specific  rotation  definitely  deter- 
mined. It  evidently  lies  between  2°  and  4°. 

There  are  three  important  aromatic  alcohols  which  have 
been  isolated  from  essential  oils  and  found  to  be  optically 
active : 

1  [al#  in  chloroform  solution,  66.32. 


MISCELLANEOUS  APPLICATIONS  269 

Terpeneol,  a  tertiary  unsaturated  alcohol  (C10H17OH), 
probably  solid  when  pure,  with  a  rotation,  in  alcoholic 
solution,  of  about  85°.  It  also  exists  in  the  inactive  or 
"  racemic  "  modification,  which  is  identical  in  its  chemical 
properties.  The  fact  that  the  isomeric  forms  exist  to- 
gether in  many  oils  makes  the  optical  determination  diffi- 
cult. Terpeneol  is  found  in  cardamom,  cajeput,  lovage, 
marjoram,  and  kuromoji  oils  among  others. 

Borneol  (C^HtfOH)  occurs  in  the  free  state  naturally  as 
the  solid  Borneo  camphor  and  in  the  levo-isomer  as  Ngai 
camphor.  It  is  also  found  as  one  or  the  other  isomer  in 
many  oils,  as  cardamom,  spike,  rosemary,  citronella,  vale- 
rian, sage,  and  thyme.  Like  the  other  alcohols,  borneol  is 
often  present  in  the  form  of  a  fatty  ester.  In  most  sol- 
vents, methyl  alcohol  being  an  exception,  both  isomers 
give  a  practically  constant  specific  rotation  of  37.70°. 

Menthol,  a  saturated  secondary  alcohol  only  found  in  the 
levo  form  as  a  constituent  of  peppermint  oils.  Long1 
gives  the  following  rotation  constants : 

The  melted  solid  at  46° : 

</44.6=  .8810  [a]/)=  -49-86°; 

alcoholic  solution  at  20° : 

[a]z>  =  —  48.247  —  .011108  q  —  .00001870^; 
benzene  solution  at  20° : 

[>]/>  =  -  49-5 1 1  -  -025634  q  -  .0008403  q* 
(q  being  the  per  cent  of  solvent). 

Of  the  aliphatic  terpene  aldehydes,  only  one  optically 
active  one  is  important : 

*/.  Am.  Chem.  Soc.,  14,  149. 


2/O  MISCELLANEOUS   APPLICATIONS 


Citronettat  (CgHtfCllO),  the  dextro-isomer  alone  having 
been  isolated.  It  is  a  constituent  of  lemon,  citronella, 
eucalyptus,  and  balm  oils  ([a]/>7.5=  12.50). 

Of  the  large  number  of  aromatic  aldehydes  which  make 
up  the  odoriferous  constituents  of  so  many  ethereal  oils,  no 
important  optically  active  ones  have  been  isolated.  The 
following  ketones  are  optically  active  : 

Carvone  (C9H16CO),  which  is  found  as  the  dextro-isomer 
([0,]^=  62.65)  in  dill  and  caraway  oils,  and  in  the  levo 
form  in  spearmint  and  kuromoji  ([a]^  =  —  62.41). 

Camphor  (C9H16CO),  besides  coming  from  its  principal 
commercial  source,  the  secretion  of  the  camphor  tree,  is  a 
constituent  of  many  plants,  such  as  sassafras,  cinnamon 
root,  spike,  and  rosemary.  The  levo-isomer  has  been 
found  in  feverfew  and  tansy.  The  specific  rotation  of 
camphor  has  been  calculated  by  Landolt  to  be  55.4°.  Lan- 
dolt  has  also  determined  the  equations  for  the  specific 
rotation  of  camphor  in  the  following  solvents  :  benzol, 
ethyl  alcohol,  dimethyl  aniline,  acetic  acid,  methyl  alcohol, 
monochloracetic  ether,  and  acetic  ether.  Benzol  is  usu- 
ally the  most  convenient  solvent  for  polarizing,  the  rotation 
formula  for  this  solvent  being  already  given  (page  262). 
The  temperature  should  be  kept  practically  constant  at 
20°,  as  changes  have  marked  influence  on  the  rotation. 

Fenchone  (C9H16CO)  much  resembles  camphor.  It  t 
found  in  fennel  as  the  dextro-isomer,  and  in  thuja  in  the 
levo  form.  The  specific  rotation  of  the  dextro-isomer  has 
been  found  to  be,  in  a  10  per  cent  alcohol  solution,  71.8°, 
the  levo-isomer  giving  —  66.9°. 

Thujone  (C9H16CO),  found  in  the  dextro  form  in  worm- 
wood, tansy,  and  sage.  The  specific  rotation  is  21.1°. 


MISCELLANEOUS   APPLICATIONS  2/1 

Pulegone  (C9H16CO)  is  found  in  pennyroyal  in  dextro 
form  ([a]/>2o  =  22.89°). 

Menthone  (C9H18CO)  occurs  in  peppermint  and  gera- 
nium oils  and  in  buchu  leaves.  Like  the  corresponding 
alcohol,  menthol,  it  is  only  found  in  the  levo  form 
([>]/*.  =  -  28.18°,  [a] ^4  =  -  27.67°). 

This  list  of  some  of  the  more  important  optically  active 
constituents  of  the  volatile  oils  is  far  from  complete,  but  it 
serves  to  indicate  the  variety  and  complexity  of  the  combi- 
nations which  make  up  these  interesting  products,  and  the 
immense  field  for  research  which  is  presented  to  the  polari- 
scopist.  Rigidly  formulated  methods  of  procedure  cannot 
be  given  for  the  investigation  of  even  the  common  essential 
oils,  but  the  analyst  must  combine  an  acquaintance  with 
the  local  conditions  of  their  production  with  an  intimate 
knowledge  of  the  chemical  composition  of  the  oil  and  its 
probable  adulterants. 

The  case  of  oil  of  lemon  will  illustrate  this  point.  The 
bulk  of  this  oil  comes  from  southern  Italy  and  Sicily. 
The  oil  from  Messina  has  a  specific  rotation  at  20°  C.  of 
59°,  or  from  some  years'  crops  even  less.  The  oil  from 
Syracuse  has  a  rotation  sometimes  as  high  as  67°.  Other 
districts  produce  oils  with  rotation  values  lying  between 
these  extremes,  the  average  being  about  60°.  Turpentine 
is  often  an  adulterant.  If  the  turpentine  is  American,  its 
specific  rotation  is  usually  about  6° ;  if  French,  —  30°.  Sub- 
stituting the  average  rotation  value  of  60°  for  the  lemon  oil 
and  the  value  for  turpentine,  when  chemical  and  physical 
tests  have  shown  which  kind  is  present,  in  the  general  equa- 
tion discussed  under  chinchona  alkaloids,  the  proportion 
of  the  adulterant  can  be  determined.  If,  however,  the 


2/2  MISCELLANEOUS   APPLICATIONS 

strongly  rotating  oil  of  orange  ([a] ^  =  98°)  has  been  added 
to  disguise  the  turpentine,  a  further  separation  must  be 
made  by  steam  distillation,  when  the  lower  boiling  turpen- 
tine will  in  the  main  distill  off  in  the  first  fraction  and  so  be 
detected  by  the  polariscope  by  the  low  rotation.  As  tem- 
perature affects  the  rotations  considerably,  polarizations 
must  be  made  at  20°. 

If  the  oil  is  known  to  be  pure,  the  polariscope  can  be 
used  to  determine  the  strength  of  an  alcoholic  solution,1  such 
as  a  lemon  flavoring  extract  for  instance,  by  a  simple  appli- 
cation of  the  principles  of  polarimetric  analysis  already 
familiar.  Such  a  method  is  in  practice. 

For  a  full  exposition  of  the  chemistry  and  analysis  of 
ethereal  oils,  see  Gildermeister  and  Hoffmann's  work  on  the 
volatile  oils,  translated  by  Kremers.  The  data  of  the 
optical  constants,  as  far  as  they  are  known,  of  some 
four  hundred  oils  are  given  in  this  work.  See  also  the 
data  given  by  Schimmel  &  Co.  in  Landolt's  "  Optische 
Drehungsvermogen,"  page  578. 

Heavy  Oils.  —  The  polariscope  has  comparatively  little 
application  in  the  chemistry  of  the  heavy  oils.  Rosin  oil, 
a  product  of  destructive  distillation  of  turpentine  residuums 
(rosins)  is  often  used  as  an  adulterant  of  the  fatty  oils  on 
account  of  its  cheapness.  The  optical  activity  of  this  oil 

1  Many  cheap  lernon  extracts  are  made  from  "  washed  "  or  "  terpeneless  " 
oil,  being  solutions  of  practically  pure  citral  made  from  oil  of  lemon  or  oil  of 
citronella  (lemon-grass)  by  distilling  off  the  low-boiling  and  optically  active 
terpenes.  Citral  is  soluble  in  dilute  alcohol,  so  that  the  expense  of  manu- 
facture is  greatly  economized.  Other  terpeneless  essential  oils  are  also  made, 
and  many  oils  are  improved  by  this  process,  as  the  terpenes  are  usually  not 
the  characteristic  odoriferous  principles,  and  the  solubility  of  the  oil  is  increased. 
The  distilled  terpenes  are  used  as  adulterants  of  pure  oils. 


MISCELLANEOUS  APPLICATIONS  273 

serves  for  its  detection.  The  greatest  difficulty  in  polari- 
metric  determinations  of  the  heavy  oils  is  in  clarifying,  as 
the  usual  methods  cause  decomposition  of  the  product,  and 
it  is  often  impossible  to  isolate  the  oil  by  distillation.  Often 
the  only  practicable  way  is  to  dilute  with  some  solvent, 
which  of  course  greatly  diminishes  the  precision  of  the 
measurements,  especially  as  the  rotations  are  as  a  rule 
small. 

Gill  and  Mason l  have  used  the  polariscope  as  an  aid  to 
the  detection  of  mineral  oil  in  the  distilled  grease  oleines 
recovered  from  wool  scouring.  These  "  oleines  "  as  wool 
oils  are  of  importance  in  the  woolen  industries,  where  they 
are  used  for  oiling  wool  preparatory  to  spinning.  As  the 
specific  rotation  of  the  unmixed  grease  lies  between  16°  and 
1 8°,  the  addition  of  the  optically  inactive2  adulterant  is 
readily  shown.  The  oil  was  diluted  with  ten  parts  of  benzol 
for  polarizing. 

Gallotannic  Acid.  —  Wood-Smith  and  Regis  have  worked 
up  a  method  for  determining  gallotannic  acid  in  tanning 
materials,  which  is  based  on  the  change  of  rotation  in  a  gela- 
tin solution,  which  has  been  clarified  with  white  of  egg, 
by  its  combination  with  gallotannic  acid.  As  the  method 
is  quite  empirical  in  its  details,  the  reader  is  referred  to  the 
original  paper  (Analyst,  23,  33). 

Tartaric  Acid  and  Tartrates.  —  E.  B.  and  F.  B.  Kenrick 3 
have  developed  methods  for  the  determination  of  tartaric 
acid  and  tartrates,  particularly  devised  for  baking  powders 
and  effervescent  mixtures.  The  authors  have  made  an 

l/.  Am.  Chem.  Soc.,  26,  665. 

2  Gill  and  Mason  found  a  very  slight  optical  activity  in  some  petroleum  oils. 
8/.  Am.  Chem.  Soc.,  24,  928. 
T 


2/4  MISCELLANEOUS   APPLICATIONS 

extensive  investigation  of  the  influence  of  many  common 
salts  and  acids  on  solutions  containing  tartaric  acid  in 
which  sugar  or  starch  is  present  or  absent.  Experiment 
showed  that  when  soluble  tartrates  or  calcium  tartrate 
were  alone  present,  and  substances  disturbing  the  rota- 
tion, like  iron  or  alumina,  were  absent,  the  rotation  of  the 
jartrate  in  an  excess  of  ammonia  was  proportional  to  the 
concentration  and  could  be  expressed  as  tartaric  acid  by 
the  following  equation,  w  =  .00519^;  x  being  the  angular 
rotation  for  the  sodium  light  in  minutes  when  the  concen- 
tration of  the  tartrate  was  about  2  grams  in  50  cubic  centi- 
meters of  ammonia  solution  containing  an  excess  no  more 
than  equivalent  to  2  cubic  centimeters  of  the  concentrated 
ammonia.  If  the  mixture  contains  the  insoluble  calcium 
tartrate,  the  mixture  must  be  dissolved  in  a  dilute  solution  of 
hydrochloric  acid  (20  drops  in  30  cubic  centimeters  of  water). 
The  solution  is  effected  by  heating  gently.  Four  cubic  centi- 
meters of  ammonia  are  added  to  the  solution  and  about  .2 
gram  of  sodium  phosphate  ;  the  mixture  is  cooled,  made  up 
to  50  cubic  centimeters,  and  filtered.  The  sodium  phosphate 
precipitates  the  lime,  and  is  not  absolutely  necessary  unless 
the  proportion  of  calcium  is  large,  when  it  prevents  the  lat- 
ter from  crystallizing  out  of  the  solution.  A  2-decimeter 
tube  is  used. 

If  sugar  is  present  in  the  mixture,  it  must  be  determined 
by  the  Clerget  method,  and  its  rotation  allowed  for.  If 
magnesium  be  present,  as  it  is  in  many  effervescent  mix- 
tures, it  must  first  be  precipitated  by  sodium  phosphate 
and  ammonia,  as  it  influences  the  rotation  values  of  both 
the  tartaric  acid  and  the  sugar.  Further,  it  is  necessary  to 
add  the  appropriate  amount  of  acid  for  inverting,  inde- 


MISCELLANEOUS   APPLICATIONS  2^ 

pendently  of  the  amount  which  goes  into  combination  with 
the  bases  present  to  free  any  organic  acids  present.  In 
this  case  an  amount  of  substance,  corresponding  to  about 
8  grams  of  substance  or  5  grams  of  sugar,  is  made  up  to 
100  cubic  centimeters ;  25  cubic  centimeters  of  this  solution 
is  put  into  a  5O-cubic-centimeter  flask,  and  if  alkaline  neu- 
tralized with  hydrochloric  acid,  using  methyl  orange  as  an 
indicator ;  i  cubic  centimeter  of  ammonia  is  added,  and  the 
solution  made  up  to  mark  and  polarized. 

The  amount  of  hydrochloric  acid  necessary  to  set  free 
any  combined  organic  acids,  and,  consequently,  not  avail- 
able as  an  inverting  agent,  is  determined  by  adding  the 
acid  to  a  second  portion  of  25  cubic  centimeters  of  the 
original  solution,  to  which  methyl  violet  has  been  added 
till  the  solution  just  turns  green,  showing  an  excess  of  the 
free  mineral  acid.  A  third  25  cubic  centimeters  of  the 
solution,  placed  in  a  5o-cubic-centimeter  flask,  is  now 
inverted  by  adding  just  the  amount  of  acid  necessary  to 
set  free  the  organic  acids,  in  addition  to  that  necessary  to 
invert,  which  is  2.5  cubic  centimeters.  The  Clerget  pro- 
cess is  carried  out  in  the  usual  way,  and,  after  cooling,  the 
acid  is  neutralized  with  ammonia,  i  cubic  centimeter  excess 
added,  and  the  solution  polarized  after  making  up  to  the 
50  mark.  The  calculation  formula  given  by  the  authors 

2(a  —  6)1.254 
is,  for  sugar,  z  = ,  a  and  b  being  expressed 

in  minutes.  The  rotation  of  the  tartaric  acid  is  x—2a  — 
79.7  #,  and  the  weight  of  acid,  w  =  4(.oos  19^). 

If  magnesium  is  present,  only  10  cubic  centimeters  of  the 
original  solution,  made  up  as  described,  containing  about 
8  grams  of  tartrate  in  100  cubic  centimeters,  is  used,  and 


276  MISCELLANEOUS   APPLICATIONS 

the  magnesium  precipitated  by  using  as  nearly  as  possible 
the  exact  amount  of  reagent  necessary;  the  precipitate 
being  removed  by  means  of  a  filter  pump  so  that  the  wash 
waters,  which  are  to  be  polarized  and  inverted,  are  reduced 
to  as  small  a  bulk  as  possible,  not  to  exceed  100  cubic 
centimeters,  to  which  the  solution  is  made  up  in  this  case. 
Twenty-five  cubic  centimeters  are  tested  to  determine  the 
amount  of  inverting  acid  necessary,  as  already  described, 
and  25  cubic  centimeters  prepared  and  inverted  in  the 
manner  also  described,  and  made  up  to  50  cubic  centi- 
meters. The  equations  in  this  case  become  : 

_  io(a  —  2^)1.254 
142  --5'      ' 
—  79.7  zy 


If  iron  or  alumina  salts  are  present,  the  polarizations  must 
be  made  in  neutral  ammonium  molybdate  solution;  the 
solution  must  be  strictly  neutral  and  phosphates  must 
be  removed.  As  the  molybdic  acid  greatly  increases  the 
rotation  of  the  tartrate,  an  amount  of  sample  containing 
only  .2  gram  of  tartrate  is  taken  in  a  dry  flask,  with 
10  cubic  centimeters  citric  acid  (c—^-^)  and  10  cubic  centi- 
meters ammonium  molybdate  (c—  -££Q),  and  allowed  to  react 
for  five  minutes,  the  flask  being  shaken  occasionally. 
Then  5  cubic  centimeters  of  magnesium  sulphate  solution 
(c=  g6_o^  and  IO  cubic  centimeters  ammonia  (165  cubic 
centimeters  ammonia,  ^=.924,  in  500  cubic  centimeters). 
These  solutions  are  exactly  measured,  making  the  volume 
35  cubic  centimeters.  If  the  substance  tested  is  a  liquid, 
allowance  for  its  volume  is  made  by  taking  less  ammonia 


MISCELLANEOUS  APPLICATIONS  277 

solution.  Within  an  hour  the  solution  is  filtered  and  20 
cubic  centimeters  measured  into  a  5o-cubic-centimeter  flask, 
and  dilute  hydrochloric  acid  added  to  faint  acidity  as  shown 
by  methyl  orange.  Ten  cubic  centimeters  of  the  molybdate 
solution  are  then  added,  and  the  whole  made  up  with  water 
to  50  cubic  centimeters.  The  solution  is  now  polarized 
after  filtering,  if  necessary,  in  a  2-decimeter  tube.  The 
specific  rotations  of  tartrates  in  neutral  molybdate  solutions 
were  found  by  the  authors  to  be  practically  constant  at 
different  concentrations.  The  equation  for  determining 
the  tartaric  acid  under  these  circumstances  is  w—. 00121  x, 
x  being,  as  in  all  the  equations  given,  the  angular  rotation 
of  sodium  light  expressed  in  minutes. 

The  author  has  had  no  experience  with  many  of  these 
methods,  but  mentions  them  as  illustrations  of  how  such 
determinations  are  worked  out.  In  the  present  state  of 
our  knowledge  of  the  optical  constants  of  many  com- 
pounds which  can  be  determined  by  polarimetric  analysis, 
it  will  be  necessary  for  the  analyst  to  devise  his  own 
method  for  the  case  at  hand.  This  should  not  be  difficult 
with  a  proper  comprehension  of  the  principles  set  forth. 
In  fact,  the  aim  in  writing  this  little  book  has  been  in  the 
main  to  show  how  these  principles  have  been  successfully 
applied,  and  to  assist  the  reader  in  acquiring  knowledge 
which  will  enable  him  to  attack  effectively  any  problem  of 
the  kind  which  comes  to  hand.  It  is  confidently  believed 
that  such  knowledge  will  greatly  extend  the  use  of  the 
polariscope  in  the  chemical  laboratory.  If  this  book  does 
its  part  in  aiding  this  extension,  it  has  not  failed  of  its 
purpose. 


APPENDIX 

BIBLIOGRAPHY  OF   THE   MORE   IMPORTANT  WORKS    OF 
REFERENCE 

General  Chemistry  of  Carbohydrates. 

Tollens.  Handbuch  der  Kohlenhydrate.  Vol.1.  1888.  Vol.11 
(supplementary).  1895.  (Contains  bibliography  of  original 
papers.) 

Maquenne.     Les  Sucres  et  principaux  De'rive's.     1900. 

Von  Lippmann.  Chemie  der  Zuckerarten.  1904.  (3d  Ed.) 
(Bibliography.) 

Technology  of  Sucrose. 

Wiley.  Bulletins  of  Division  of  Chemistry,  United  States  Depart- 
ment of  Agriculture. 

(Cane  Sugar  and  Sorghum),  2,  3,  5,  6,  8,  14,  17. 

(Sorghum),  20,  26,  29,  34,  37,  40. 

(Beet  Sugar),  27,  30,  33,  36,  39,  72,  52  (revised),  64,  78 

Also  Special  Reports,  1897,  1898,  1899. 
(Sugar  Producing  Plants),  18. 
Spencer.     (Cane  Sugar),  ibid,  n,  15,  21. 
Crampton.      (Cane  Sugar),  ibid.  22. 
Edson.     (Cane  Sugar),  ibid.  23. 

Basset.     Guide  pratique  du  Fabricant  de  Sucre.     1882. 
Horsin-D£on.     Fabrication  de  Sucre.     1882. 
Lock  and  Newlands  Bros.     Handbook  for  Planters  and  Sugar 

Manufacturers.     1888. 

Von  Lippmann.  Geschichte  des  Zuckers.  1890. 
Roth.  Literature  of  Sugar.  1890  (bibliography). 
Watts.  An  Introductory  Manual  for  Sugar  Growers.  1893. 

279 


280  APPENDIX 

Beaudet-Pellet-Saillard.     Traite"  de  la  Fabrication  du  Sucre.    1894. 
Stubbs.     Sugar  Cane  (Vol.  I).    The  Chemistry  and  Manufacture  of 

Sugar  (Vol.  II).     1897. 

Horsin-D£on.     Le  Sucre  et  PIndustrie  sucriere.     1894. 
Stohmann.     Zuckerfabrikation.     (4th  Ed.)      1899. 
Sadtler.     Handbook  of  Industrial  Organic  Chemistry.     (3d  Ed.) 

1900. 

Deerr.     Sugar  House  Notes  and  Tables.     1900. 
Bass.     Cane  Sugar  (English  and  Spanish  text).     1901.    (2dEd.) 
Geschwind  et  Sellier.     La  Betterave.     1902. 
Quivy.     L'Epuration  des  Jus  Sucre's  par  Electricite.     1902. 
Mittelstaedt.     Aus  der  Praxis  der  Zuckerindustrie.     1902. 
Prinsen-Geerligs.     On  Cane  Sugar.     1903.     (2d  Ed.) 
Teyssier.     Fabrication  du  Sucre.     1904. 
Stillman.     Cane   Sugar   Machinery  (English   and   Spanish  text). 

1904. 

Mackintosh.     Technology  of  Sugar.     1904. 
Claassen.     Die  Zuckerfabrikation.     1904. 
Colsen.     Culture  Industrie  de  la  Canne  a  Sucre  aux  Isles  Hawai, 

(2d  Ed.)      1905. 
Thorp.     Outlines  of  Industrial  Chemistry.     (2d  Ed.)     1905. 

Periodicals  of  Sugar  Technology. 

Zeitschrift  des  Vereins  der  deutschen  Zuckerindustrie. 

Neue  Zeitschrift  fur  Rubenzuckerindustrie. 

Stammer.     Jahrsbericht  der  Zuckerfabrikation. 

Bulletin  de  PAssociation  des  Chimistes  de  Sucrerie  et  de  Distillation 

The  Louisiana  Sugar  Planter  and  Sugar  Manufacturer. 

The  Hawaiian  Planter's  Monthly. 

The  Sugar  Cane.     (British.) 

Die  Deutsche  Zuckerindustrie. 

Centralblatt  flir  die  Zuckerindustrie. 

Osterreichisch-Ungarische  Zeitschrift  fur  Zuckerindustrie  (etc.). 


APPENDIX  28l 

La  Sucrerie  Beige. 

Zeitschrift  fur  Zuckerindustrie  in  Bohmen. 

Analytical  Methods  and  Chemical  Control  of  Sugar  (sucrose] 
Manufacture. 

Spencer.  Handbook  for  Sugar  Manufacturers.  (Cane  Sugar.) 
1889. 

Tucker.     Manual  of  Sugar  Analysis.     1890. 

Wiechmann.     Sugar  Analysis.     1890. 

Sidersky.     Traite*  d'Analyse  der  Materieres  sucre*es.     1890. 

Steydn.  Die  Untersuchungen  der  Zuckers  und  Zuckerhaltigen 
Stone.  1893. 

Wiley.  Principles  and  Practice  of  Agricultural  Chemical  Analysis. 
1896. 

Peffer.     Beet  Sugar  Analysis.     1897. 

Spencer.     Handbook  for  Beet-sugar  Manufacturers.     1897. 

Sidersky.     Aide-M£moire  de  Sucre* rie.     1898. 

Broquet  and  Dethier.  Manuel  d'Analyse  Chimique  1'Usage  des 
Fabricants  de  Sucre.  1898. 

United  States  Treasury.  Bulletin  2113.  Revised  Regulations 
governing  the  Sampling  and  Classification  of  Imported 
Sugars  and  Molasses.  1899. 

Fruhling.  Anleitung  zur  Untersuchung  der  fur  die  Zuckerindus- 
trie in  Betracht  kommenden.  Rohmaterialien,  Produkte, 
Neben  Produkten  und  Hilfssubstanzen.  (6th  Ed.)  1903. 

Stolle.     Handbuch  fur  zuckerfabriks  Chemiker.     1904. 

Morse.     Calculations  used  in  Cane-sugar  Factories.     1904. 

Lactose.     Analytic  Methods. 

Wiley.     Principles  and  Practice  of  Agricultural  Chemical  Analysis. 

Vol.  III.     1896. 
United  States  Department  of  Agriculture — Division  of  Chemistry. 

Bulletin  46.     (Revised.) 


282  APPENDIX 

Starch  and  Starch  Products  —  Analytic  and  Technical. 

Wagner.     Starkefabrikation.     1886. 

Birnbaum.     Starkezucker.     1886. 

National  Academy  of  Sciences.     Report  on  Glucose.     1884 

Fritsch.     La  Fecule.     1890. 

Griffiths.     Principal  Starches  used  as  Food.    (Photomicrographs., 

1892. 

Saare.     Fabrikation  de  Kartoffelstarke.     1897. 
Sadtler.     Handbook  of  Industrial  Organic  Chemistry.     1900. 
Heron.     Thorpe's  Dictionary  of  Applied  Chemistry.      (Articles, 

"  Sugar  "  and  "  Starch.")    1900. 
O'Sullivan  and  Heron.     Ibid.     Articles,  "Dextrin,"  "Dextrose," 

and  "  Maltose." 
Bersch.     Die  Fabrikation  von  Starkezucker,  Dextrin,  Zuckercoleur 

und  Invertzucker.     1901. 

Thorp.     Outlines  of  Industrial  Chemistry.     (2d  Ed.)     1905. 
Wiley.     (Cassava  and  Potato   Starch.)     Bulletin   of  Division  of 

Chemistry,  United  States  Department  of  Agriculture,  44  and  58. 

Sugar  Analysis  applied  to  Brewing. 

Moritz  and  Morris.     Text-book  of  the  Science  of  Brewing.    1890. 

Prior.     Maltz  und  Bier.     1896. 

Brown  (Adrian).    Laboratory  Studies  for  Brewing  Students.    1904. 

Polarimetric  Methods  in  Food  Analysis. 

Leach.     Food  Inspection  and  Analysis.     1904. 
United  States  Department  of  Agriculture  —  Division  of  Chemistn 
Bulletins  46  (revised),  65,  and  66.     1902. 

Polarimetric  Methods  applied  to  Essential  Oils  and  Drugs. 

Allen.     Commercial  Organic  Analysis.     Vol.  Ill,  Part  2.     1892. 
Parry.     The  Chemistry  of  the  Essential  Oils  and  Artificial  Per- 
fumes.    1899. 


APPENDIX  283 

Gildermeister   and    Hoffmann.     (Translated  by  Kremers.)     The 
Volatile  Oils.     1902. 

Optics  of  the  Polariscope  and  General  Theoretical  Principles. 

Tyndall.     Notes  on  Light.     1882. 

Landolt.     Das  optische  Drehungsvermogen.     1898. 

Preston.     Theory  of  Light.     (3d  Ed.)      1901. 

Landolt.     (Translated  by  Long.)     Optical  Rotation  of  Organic 

Substances.     1902. 
Heron.     Thorpe's   Dictionary   of   Applied   Chemistry.     (Article, 

"  Sugar  "  ;  section,  "  Saccharimetry.")    (Excellent  exposition 

of  whole  subject.) 


TABLES 

.— HYDROiMETER  TABLE   FOR   AQUEOUS   SUGAR   SOLUTIONS 
AT   I7.5°C. 

(Specific  gravity  referred  to  water  at  17.5°) 


DEGREES 
BRIX 

SPECIFIC  /  ,  17.5\ 
GRAVITY  V    17.5/ 

DEGREES 
BAUME 

DEGREES 
BRIX 

SPECIFIC  /  ,  17.5\ 
GRAVITY  \a  17.5/ 

DEGREES 
BAUME 

o.o 

1.  00000 

0.00 

4.0 

1.01570 

2  27 

O.I 

1.00038 

0.06 

4.1 

.01610 

2-33 

O.2 

1.00077 

O.I  I 

4.2 

.01650 

238 

o-3 

1.00116 

0.17 

4-3 

.01690 

2-44 

0.4 

1.00155 

0.23 

4.4 

.01730 

2.50 

°-5 

1.00193 

0.28 

4-5 

.01770 

2-55 

0.6 

1.00232 

0-34 

4.6 

.01810 

2.61 

0.7 

1.00271 

0.40 

4-7 

.01850 

2.67 

0.8 

1.00310 

0-45 

4.8 

.01890 

2.72 

0.9 

1.00349 

0.51 

4.9 

.01930 

2.78 

I.O 

1.00388 

0-57 

5-0 

.01970 

2.84 

I.I 

1.00427 

0.63 

5-1 

.02010 

2.89 

.2 

1  .00466 

0.68 

5-2 

.02051 

2.95 

•3 

1.00505 

0.74 

5-3 

.02091 

3.01 

•4 

1.00544 

0.80 

5-4 

.02131 

3.06 

•5 

1.00583 

0.85 

5-5 

.02171 

3.12 

.6 

1.00622 

0.91 

5-6 

.O22I  I 

3.18 

•7 

1.00662 

0.97 

5-7 

1.02252 

3.23 

.8 

1.00701 

1.02 

5-8 

I  .O2292 

3.29 

•9 

1.00740 

1.  08 

5-9 

L02333 

3-35 

2.0 

1.00779 

I.I4 

6.0 

1.02373. 

3-40 

2.1 

1.00818 

I.I9 

6.1 

I.024I3 

3-46 

2.2 

1.00858 

1.25 

6.2 

1.02454 

3-52 

2-3 

1.00897 

I-31 

6-3 

1.02494 

3-57 

2.4 

1.00936 

1-36 

6.4 

L02535 

3.63 

2.5 

1.00976 

1.42 

6-5 

1.02575 

3-69 

2.6 

1.01015 

1.48 

6.6 

I.026l6 

3-74 

2.7 

1.01055 

i-53 

6.7 

1  .02657 

3-80 

2.8 

1.01094 

i-59 

6.8 

1.02697 

3.86 

2.9 

1.01134 

1.65 

6.9 

1.02738 

3-91 

3-0 

1.01173 

1.70 

7.0 

1.02779 

3-97 

3.1 

1.01213 

1.76 

7-1 

I.028I9 

4.03 

3-2 

1.01252 

1.82 

7.2 

1.02860 

4.08 

3-3 

1.01292 

1.87 

7-3 

I.0290I 

4.14 

3-4 

1.01332 

i-93 

7-4 

1.02942 

4.20 

3-5 

1.01371 

1.99 

7-5 

1.02983 

4.25 

3-6 

1.01411 

2.04 

7.6 

1  .03024 

4-31 

3-7 

1.01451 

2.10 

7-7 

1.03064 

4-37 

3-8 

1.01491 

2.l6 

7.8 

I.03I05 

4-42 

3-9 

1.01531 

2.21 

7-9 

1.03146 

4.48 

285 


286 


TABLES 


DEGREES 
BRIX 

SPECIFIC  /  ,  17.5\ 
GRAVITY  \    17.57 

DEGREES 

BAUMfe 

DEGREES 
BRIX 

SPECIFIC  /  ,  17.5\ 
GRAVITY  \a  17.5/ 

DEGREES 
BAUME 

8.0 

1.03187 

4-53 

13.0 

1.05276 

7.36 

8.1 

1.03228 

4-59 

I3.I 

1.05318 

7.41 

8.2 

1  .03270 

4.65 

13.2 

1.05361 

7-47 

8-3 

1.03311 

4.70 

13-3 

1.05404 

7-53 

8.4 

1.03352 

4.76 

13-4 

1.05446 

7.58 

8-5 

1-03393 

4.82 

13-5 

1.05489 

7.64 

8.6 

1.03434 

4.87 

13-6 

L05532 

7-69 

8-7 

1-03475 

4-93 

13-7 

1-05574 

7-75 

8.8 

I-035I7 

4.99 

13-8 

1.05617 

7.81 

8.9 

I-03558 

5.04 

13-9 

1.05660 

7.86 

9.0 

1  -03599 

5.10 

14.0 

1.05703 

7.92 

9-1 

1  .03640 

5.16 

14.1 

1.05746 

7.98 

9.2 

1.03682 

5-21 

14.2 

1.05789 

8.03 

9-3 

1.03723 

5-27 

14-3 

1.05831 

8.09 

9.4 

1.03765 

5.33 

14.4 

1.05874 

8.14 

9-5 

1.03806 

5.38 

14-5 

1.05917 

8.20 

9.6 

1.03848 

5-44 

14.6 

1.05960 

8.26 

9-7 

1.03889 

5.50 

14.7 

1.06003 

8.31 

9.8 

1.03931 

5-55 

14.8 

1.06047 

8.37 

9-9 

1.03972 

5.6i 

14.9 

1.06090 

8.43 

IO.O 

1.04014 

5.67 

15-0 

1.06133 

8.48 

10.  1 

1.04055 

5-72 

I5-I 

1.06176 

8.54 

10.2 

1.04097 

5.78 

15-2 

1.06219 

8.59 

10.3 

1.04139 

5.83 

J5.3 

1.06262 

8.65 

10.4 

1.04180 

5.89 

15-4 

i  .06306 

8.71 

10.5 

1.04222 

5-95 

15.5 

1.06349 

8.76 

10.6 

1.04264 

6.00 

15.6 

1.06392 

8.82 

10.7 

1.04306 

6.06 

15-7 

1.06436 

8.88 

10.8 

1.04348 

6.12 

15.8 

1.06479 

8.93 

10.9 

1.04390 

6.17 

15-9 

1.06522 

8.99 

II  .0 

1,04431 

6.23 

16.0 

1.06566 

9-04 

n.  i 

1.04473 

6.29 

16.1 

1.06609 

9.10 

II.  2 

1-04515 

6.34 

16.2 

1.06653 

9.16 

"•3 

1-04557 

6.40 

16.3 

1.06696 

9.21 

11.4 

1.04599 

6.46 

16.4 

1.06740 

9.27 

ii-5 

1.04641 

6.51 

16.5 

1.06783 

9-33 

II.6 

1.04683 

6.57 

16.6 

1.06827 

9.38 

11.7 

1.04726 

6.62 

16.7 

1.06871 

9-44 

n.8 

1.04768 

6.68 

16.8 

1.06914 

9.49 

11.9 

1.04810 

6.74 

16.9 

1.06958 

9-55 

12.0 

1.04852 

6.79 

17.0 

1.07002 

9.61 

12.  1 

1.04894 

6.85 

17.1 

i  .07046 

9.66 

12.2 

1.04937 

6.91 

17.2 

1.07090 

9.72 

12.3 

1.04979 

6.96 

17.3 

1.07133 

9-77 

12.4 

1.05021 

7.02 

17.4 

1.07177 

9.83 

12.5 

1.05064 

7.08 

!7-5 

1.07221 

9.89 

12.6 

1.05106 

7.13 

17.6 

1.07265 

9-94 

I2.7 

1.05149 

7.19 

17.7 

1.07309 

10.00 

12.8 

1.05191 

7.24 

17.8 

1.07353 

10.  06 

12.9 

1.05233 

7-30 

17.9 

1.07397 

10.  II 

TABLES 


287 


DEGREES 
BRIX 

SPECIFIC  /  ,  17.5\ 
GRAVITY  \    17  .5/ 

DEGREES 
BAUME 

DEGREES 
BRIX 

SPECIFIC  /  ,  17.5\ 
GRAVITY  \d  m) 

DEGREES 
BAUME 

18.0 

1.07441 

10.17 

23.0 

1.09686 

12.96 

18.1 

1.07485 

10.22 

23.1 

1.09732 

13.02 

18.2 

1.07530 

10.28 

23.2 

1.09777 

13.07 

18.3 

1.07574 

10.33 

23-3 

1.09823 

13.13 

18.4 

1.07618 

10.39 

23-4 

1.09869 

I3.I9 

18.5 

1  .07662 

10.45 

23-5 

1.09915 

13.24 

18.6 

1.07706 

10.50 

23.6 

1.09961 

I3-30 

18.7 

1.07751 

10.56 

23-7 

1.10007 

13-35 

18.8 

1-07795 

10.62 

23.8 

1.10053 

I3-4I 

18.9 

1.07839 

10.67 

23-9 

1.10099 

13.46 

19.0 

1.07884 

10.73 

24.0 

1.10145 

I3-52 

19.1 

1.07928 

10.78 

24.1 

1.10191 

I3-58 

19.2 

1.07973 

10.84 

24.2 

1.10237 

13-03 

19-3 

1.08017 

10.90 

24-3 

1.10283 

13.69 

19.4 

1.08062 

10.95 

24.4 

1  .  10329 

13-74 

19-5 

1.  08106 

II.  01 

24-5 

1-10375 

13.80 

19.6 

1.08151 

1  1.  06 

24.6 

1.10421 

J3-95 

19.7 

1.08196 

II.  12 

24-7 

1.10468 

13-91 

19.8 

1.08240 

II.I8 

24,8 

1.10514 

13.96 

19.9 

1.08285 

11.23 

24.9 

1.10560 

14.02 

20.0 

1.08329 

11.29 

25.0 

1.10607 

14.08 

20.1 

1.08374 

"•34 

25.1 

1.10653 

14-13 

20.2 

1.08419 

11.40 

25.2 

1.10700 

14.19 

20.3 

1.08464 

n-45 

25-3 

1.10746 

14.24 

20.4 

1.08509 

11.51 

25-4 

1.10793 

14.30 

20.5 

1.08553 

JI-57 

25-5 

1.10839 

14-35 

20.6 

1.08599 

11.62 

25.6 

1.10886 

14.41 

20.7 

1.08643 

11.68 

25-7 

1.10932 

14.47 

20.8 

1.08688 

"•73 

25.8 

1.10979 

14.52 

20.9 

1.08733 

11.79 

25-9 

1.11026 

14.58 

21.0 

1.08778 

11.85 

26.0 

1.11072 

14.63 

21.  1 

1.08824 

11.90 

26.1 

1.11119 

14.69 

21.2 

1.08869 

11.96 

26.2 

1.11166 

14.74 

21.3 

1.08914 

12.01 

26.3 

1.11213 

14.80 

21.4 

1.08959 

12.07 

26.4 

1.11259 

14.85 

21.5 

1.09004 

12.13 

26.5 

1.11306 

14.91 

21.6 

1.09049 

I2.I8 

26.6 

I-II353 

14.97 

21.7 

1.09095 

12.24 

26.7 

1.11400 

15.02 

21.8 

1.09140 

12.29 

26.8 

1.11447 

15.08 

21.9 

1.09185 

12-35 

26.9 

1.11494 

15-13 

22.0 

1.09231 

12.40 

27.0 

1.11541 

^3-^9 

22.1 

1.09276 

12.46 

27.1 

1.11588 

15.24 

22.2 

1.09321 

12.52 

27.2 

1-11635 

I5-30 

22.3 

1.09367 

12-57 

27-3 

1.11682 

J5-35 

22.4 

1.09412 

12.63 

27-4 

1.11729 

i5-4i 

22.5 

1.09458 

12.68 

27.5 

1.11776 

1546 

22.6 

1.09503 

12.74 

27.6 

1.11824 

15-52 

22.7 

1.09549 

12.80 

27.7 

1.11871 

X5.58 

22.8 

1-09595 

12.85 

27.8 

1.11918 

15.63 

22.9 

i  .09640 

12.91 

27.9 

1.11965 

15.69 

288 


TABLES 


DEGREES 
BRIX 

SPECIFIC  /  ,  17.5\ 
GRAVITY  \a  17.5/ 

DEGREES 

BAUME 

DEGREES 
BRIX 

SPECIFIC  /  ,  17.5\ 
GRAVITY  V    17.5/ 

DEGREES 
BAUME 

28.0 

1.12013 

15-74 

33-o 

1.14423 

18.50 

28.1 

.12060 

15.80 

33-1 

1.14472 

18.56 

28.2 

.12107 

15-85 

33-2 

1.14521 

18.61 

28.3 

•12155 

I5-9I 

33-3 

1.14570 

18.67 

28.4 

.12202 

15.96 

33-4 

1.14620 

18.72 

28.5 

.12250 

16.02 

33-5 

1.14669 

18.78 

28.6 

.12297 

16.07 

33-6 

1.14718 

18.83 

28.7 

•12345 

16.13 

33-7 

1.14767 

18.89 

28.8 

•I2393 

16.18 

33-8 

1.14817 

18.94 

28.9 

.12440 

16.24 

33-9 

1.14866 

19.00 

29.0 

.12488 

16.30 

34-0 

1.14915 

19.05 

29.1 

•12536 

16.35 

34-1 

1.14965 

19.11 

29.2 

•12583 

16.41 

34-2 

1.15014 

19.16 

29-3 

.12631 

16.46 

34-3 

1.15064 

19.22 

29.4 

.12679 

16.52 

34-4 

I.I5II3 

19.27 

29-5 

.12727 

16-57 

34-5 

1.15163 

19-33 

29.6 

•12775 

16.63 

34-6 

1.15213 

19.38 

29.7 

.12823 

16.68 

34-7 

1.15262 

19.44 

29.8 

.12871 

16.74 

34-8 

1.15312 

19.49 

29.9 

.12919 

16.79 

34-9 

1.15362 

19-55 

30.0 

.12967 

16.85 

35-o 

1.15411 

19.60 

30.1 

•13015 

16.90 

35-1 

1.15461 

19.66 

30.2 

.13063 

16.96 

35-2 

I.I55" 

19.71 

30.3 

13111 

17.01 

35-3 

I.I556I 

19.76 

3°-4 

•I3IS9 

17.07 

35-4 

1.15611 

19.82 

3°-5 

.13207 

17.12 

35-5 

1.15661 

19.87 

30.6 

•I3255 

17.18 

35-6 

1.15710 

19.93 

3°-7 

•i3304 

17.23 

35-7 

1.15760 

19.98 

30.8 

•13352 

17.29 

35-8 

1.15810 

20.04 

30-9 

.13400 

17-35 

35-9 

1.15861 

20.09 

31.0 

•13449 

17.40 

36.0 

1.15911 

20.15 

31-1 

•13497 

17.46 

36.1 

1.15961 

20.20 

31.2 

•13545 

17.51 

36.2 

1.  16011 

20.26 

3*-3 

•13594 

17-57 

36.3 

1.  16061 

20.31 

3x-4 

.13642 

17.62 

36-4 

i.i6m 

20.37 

3*-5 

.13691 

17.68 

36.5 

1.16162 

20.42 

31.6 

.13740 

17*73 

36.6 

1.16212 

20.48 

3J-7 

.13788 

17.79 

36.7 

1.16262 

20.53 

31-8 
3x-9 

•13837 
•13885 

17.84 
17.90 

36.8 
36-9 

1.16313 
1.16363 

20.59 
20.64 

32.0 

•13934 

17-95 

37-o 

1.16413 

20.70 

32.1 

•i3983 

18.01 

37-i 

1.16464 

20.75 

32.2 

.14032 

1  8.  06 

37-2 

1.16514 

20.80 

32.3 

.14081 

18.12 

37-3 

1.16565 

20.86 

32.4 

.14129 

18.17 

37-4 

1.  16616 

20.91 

32-5 

.14178 

18.23 

37-5 

1.16666 

20.97 

32.6 

.14227 

18.28 

37-6 

1.16717 

21.02 

32.7 

.14276 

18.34 

37-7 

1.16768 

21.  08 

32.8 

•14325 

18.39 

37-8 

1.  16818 

21.13 

32-9 

•14374 

18.45 

37-9 

1.16869 

21.19 

TABLES 


289 


DEGREES 
BRIX 

SPECIFIC  /  ,  17".5\ 
GRAVITY  \a  17..V 

DEGREES 
BAUME 

DEGREES 
BRIX 

SPECIFIC  /  ,  17.5\ 
GRAVITY  \    17.57 

DEGREES 

BAUMlf 

38.0 

1.16920 

21.24 

43-0 

LI9505 

23.96 

38.1 

1.16971 

21.30 

43-1 

LI9558 

24.01 

38.2 

1.17022 

2L35 

43-2 

1.19611 

24.07 

38.3 

1.17072 

21.40 

43-3 

.19663 

24.12 

38.4 

1.17123 

21.46 

43-4 

.19716 

24.17 

38.5 

1.17174 

21.51 

43-5 

.19769 

24.23 

38.6 

1.17225 

21-57 

43-6 

.19822 

24.28 

38.7 

1.17276 

21.62 

43-7 

.19875 

24-34 

38.8 

1.17327 

21.68 

43-8 

.19927 

24.39 

38.9 

1.17379 

21.73 

43-9 

.19980 

24.44 

39-o 

1.17430 

21.79 

44.0 

.20033 

24.50 

39-1 

1.17481 

21.84 

44.1 

.20086 

24.55 

39-2 

LI7532 

21.90 

44.2 

.20139 

24.61 

39-3 

LI7583 

21.95 

44-3 

.20192 

24.66 

39-4 

LI7635 

22.00 

44-4 

•20245 

24.71 

39-5 

1.17686 

22.O6 

44-5 

.20299 

24.77 

39-6 

1.17737 

22.11 

44-6 

.20352 

24.82 

39-7 

1.17789 

22.17 

44-7 

.20405 

24.88 

39-8 

1  .  17840 

22.22 

44.8 

.20458 

24.93 

39-9 

1.17892 

22.28 

44-9 

.20512 

24.98 

40,0 

I-I7943 

22.33 

45-o 

.20565 

25.04 

40.1 

I-I7995 

22.38 

45-1 

.20618 

25.09 

40.2 

1.18046 

22.44 

45-2 

.20672 

25.14 

40.3 

1.18098 

22.49 

45-3 

•20725 

25.20 

40.4 

1.18150 

22.55 

45-4 

.20779 

25.25 

40-5 

1.18201 

22.60 

45-5 

.20832 

25-31 

40.6 

1.18253 

22.66 

45-6 

.20886 

25-36 

40.7 

1.18305 

22.71 

45-7 

.20939 

25.41 

40.8 

LI8357 

22.77 

45-8 

.20993 

25.47 

40.9 

1.18408 

22.82 

45-9 

.21046 

25.52 

41.0 

1.18460 

22.87 

46.0 

.21100 

25-57 

41.1 

1.18512 

22.93 

46.1 

.21154 

25.63 

41.2 

1.18564 

22.98 

46.2 

.21208 

25.68 

41-3 

1.  18616 

23.04 

46-3 

.21261 

25.74 

41.4 

1.18668 

23.09 

46.4 

.21315 

25.79 

4i-5 

1.18720 

23.15 

46.5 

21369 

25.84 

41.6 

1.18772 

23.20 

46.6 

.21423 

25.90 

41.7 

1.18824 

23.25 

46-7 

.21477 

25.95 

41.8 

1.18877 

23.31 

46.8 

.21531 

26.00 

41.9 

1.18929 

23.36 

46.9 

.2I585 

26.06 

42.0 

1.18981 

23.42 

47.0 

.21639 

26.11 

42.1 

1.19033 

23.47 

47.1 

.21693 

26.17 

42.2 

1.19086 

23.52 

47.2 

•21747 

26.22 

42-3 

I  19138 

23.58 

47.3 

.2l802 

26.27 

42.4 

1.19190 

23.63 

47-4 

.21856 

26.33 

42.5 

1.19243 

23.69 

47-5 

.2I9IO 

26.38 

42.6 

1.19295 

23.74 

47-6 

.21964 

26.43 

42-7 

1.19348 

23.79 

47-7 

.22019 

26.49 

42.8 

1.19400 

23.85 

47.8 

•22073 

26.54 

42.9 

I-I9453 

23.90 

47-9 

.22127 

26.59 

290 


TABLES 


DEGREES 
BRIX 

SPECIFIC  /  ,  17.5\ 
GRAVITY  \a  u.5/ 

DEGREES 
BAUME 

DEGREES 
BRIX 

SPECIFIC  /  ,  17.5\ 
GRAVITY  \    17.57 

DEGREES 
BAUME 

48.0 

1.22182 

26.65 

53-0 

1.24951 

29.31 

48.1 

1.22236 

26.70 

53-1 

1.25008 

29.36 

48.2 

1.22291 

26.75 

53-2 

1.25064 

29.42 

48.3 

1-22345 

26.81 

53-3 

1.25120 

29-47 

48.4 

1.22400 

26.86 

534 

1.25177 

29-52 

48.5 

1-22455 

26.92 

53-5 

1.25233 

29-57 

48.6 

1.22509 

26.97 

53-6 

1.25290 

29.63 

48.7 

1.22564 

27.02 

53-7 

1-25347 

29.68 

48.8 

1.22619 

27.08 

53-8 

1.25403 

29-73 

48.9 

1.22673 

27.13 

53-9 

1.25460 

29-79 

49.0 

1.22728 

27.18 

54-0 

I.255I7 

29.84 

49.1 

1.22783 

27.24 

54-i 

1-25573 

29.89 

49.2 

1.22838 

27.29 

54-2 

1.25630 

29.94 

49-3 

1.22893 

27-34 

54-3 

1.25687 

30.00 

49.4 

1.22948 

27.40 

54-4 

1.25744 

3°-°5 

49-5 

1.23003 

27-45 

54-5 

1.25801 

30.10 

49.6 

1.23058 

27.50 

54-6 

1.25857 

30.16 

49-7 

1.23113 

27.56 

54-7 

1.25914 

30.21 

49.8 

1.23168 

27.61 

54-8 

1.25971 

30.26 

49-9 

1.23223 

27.66 

54-9 

1.26028 

30-31 

50.0 

1.23278 

27.72 

55-0 

1.26086 

30.37 

50.1 

1-23334 

27.77 

55-i 

1.26143 

30.42 

50.2 

1.23389 

27.82 

55-2 

1.26200 

30.47 

50.3 

1.23444 

27.88 

55-3 

1.26257 

30.53 

5o.4 

1.23499 

27.93 

55-4 

1.26314 

30-58 

50-5 

1.23555 

27.98 

55-5 

1.26372 

30.63 

50.6 

1.23610 

28.04 

55-6 

1.26429 

30.68 

50-7 

1.23666 

28.09 

55-7 

1.26486 

30.74 

50.8 

1.23721 

28.14 

55-8 

1.26544 

30.79 

50-9 

1.23777 

28.20 

55-9 

1.26601 

30.84 

51.0 

1.23832 

28.25 

56.0 

1.26658 

30.89 

51-1 

1.23888 

28.30 

56.1 

1.26716 

30.95 

51-2 

1.23943 

28.36 

56.2 

1.26773 

31.00 

5J-3 

1.23999 

28.41 

56-3 

1.26831 

31-05 

5^4 

1.24055 

28.46 

56.4 

1.26889 

31.10 

5J-5 

1.24111 

28.51 

56.5 

1.26946 

31.16 

51-6 

1.24166 

28.57 

56.6 

1.27004 

31.21 

S*'7 

1.24222 

28.62 

56.7 

1.27062 

31.26 

51-8 

1.24278 

28.67 

56.8 

1.27120 

3i-3i 

Si-9 

1-24334 

28.73 

56-9 

1.27177 

31-37 

52.0 

1.24390 

28.78 

57-0 

1.27235 

3142 

52-1 

1.24446 

28.83 

57-i 

1.27293 

31-47 

52.2 

1.24502 

28.89 

57-2 

I.2735I 

31-52 

52.3 

1.24558 

28.94 

57-3 

1.27409 

3I-58 

52.4 

1.24614 

28.99 

57-4 

1.27467 

31-63 

52.5 

1.24670 

29.05 

57-5 

1-27525 

31.68 

52.6 

1.24726 

29.10 

57-6 

1-27583 

31-73 

52.7 

1.24782 

29.15 

57-7 

1.27641 

31.79 

52.8 

1.24839 

29.20 

57-8 

1.27699 

31.84 

52-9 

1.24895 

29.26 

57-9 

1.27758 

31-89 

TABLES 


291 


DEGREES 
BRIX 

SPECIFIC  /  .  17.5\ 
GRAVITY  \    17.5/ 

DEGREES 
BAUME 

DEGREES 
BRIX 

SPECIFIC  /  r  17.5\ 
GRAVITY  \    17.5/ 

DEGREES 
BAUME 

58.0 

1.27816 

31-94 

63.0 

1.30777 

34-54 

58.1 

1.27874 

32.00 

63-1 

1.30837 

34-59 

58.2 

1.27932 

32.05 

63.2 

1.30897 

34-65 

58.3 

1.27991 

32.10 

63-3 

1.30958 

34-70 

58.4 

1.28049 

32.15 

63-4 

1.31018 

34-75 

58.5 

1.28107 

32.20 

63-5 

1.31078 

„    34-80 

58.6 

1.28166 

32.26 

63.6 

I.3H39 

34-85 

58.7 

1.28224 

32.31 

63-7 

1.31199 

34-90 

58.8 

1.28283 

32-36 

63.8 

1.31260 

34-96 

58.9 

1.28342 

32.41 

63-9 

1.31320 

35-01 

59-0 

1.28400 

32.47 

64.0 

1.31381 

35.o6 

59-1 

1.28459 

32.52 

64.1 

1.31442 

35." 

59-2 

1.28518 

32.57 

64.2 

1.31502 

35-16 

59-3 

1.28576 

32.62 

64-3 

1-31563 

35-21 

59-4 

1.28635 

32.67 

64.4 

1.31624 

35-27 

59-5 

1.28694 

32.73 

64-5 

1.31684 

35-32 

59-6 

1-28753 

32.78 

64.6 

L3I745 

35-37 

59-7 

1.28812 

32.83 

64.7 

1.31806 

35.42 

59-8 

1.28871 

32.88 

64.8 

1.31867 

35-47 

59-9 

1.28930 

32.93 

64.9 

1.31928 

35-52 

60.0 

1.28989 

32.99 

65.0 

1.31989 

35-57 

60.  i 

1.29048 

33-04 

65-1 

1.32050 

35.63 

60.2 

1.29107 

33.09 

65.2 

1.32111 

35-68 

60.3 

1.29166 

33-14 

65-3 

1.32172 

35-73 

60.4 

1.29225 

33-20 

65-4 

1.32233 

35-78 

60.5 

1.29284 

33-25 

65-5 

1.32294 

35.83 

60.6 

L29343 

33.30 

65.6 

I.32355 

35-88 

60.7 

1.29403 

33-35 

65-7 

1.32417 

35-93 

60.8 

1.29462 

33-40 

65.8 

1.32478 

35-98 

60.9 

1.29521 

33-46 

65.9 

1-32539 

36.04 

61.0 

1.29581 

33  -5  1 

66.0 

1.32601 

36.09 

61.1 

1.29640 

33.56 

66.1 

1.32662 

36.14 

61.2 

1.29700 

33-61 

66.2 

1.32724 

36.19 

61.3 

1.29759 

33-66 

66.3 

1-32785 

36.24 

61.4 

1.29819 

33-71 

66.4 

1.32847 

36.29 

61-5 

1.29878 

33-77 

66.5 

1.32908 

36.34 

61.6 

1.29938 

33-82 

66.6 

1.32970 

36.39 

61.7 

1.29998 

33.87 

66.7 

1.33031 

36.45 

61.8 

1.30057 

33-92 

66.8 

L33093 

36-50 

61.9 

1.30117 

33-97 

66.9 

I.33I55 

36.55 

62.0 

1.30177 

34.03 

67.0 

1.33217 

36.60 

62.1 

1.30237 

34.08 

67.1 

1,33278 

36.65 

62.2 

1.30297 

34-13 

67.2 

1-33340 

36.70 

62.3 

1.30356 

34.18 

67-3 

1.33402 

36.75 

62.4 

1.30416 

34-23 

67-4 

1.33464 

36.80 

62.5 

1.30476 

34.28 

67-5 

1.33526 

36-85 

62.6 

1.30536 

34-34 

67.6 

1.33588 

36-90 

62.7 

1.30596 

34-39 

67-7 

1.33650 

36.96 

62.8 

1.30657 

34-44 

67.8 

1.33712 

37.01 

62.9 

1.30717 

34-49 

67.9 

1-33774 

37-06 

TABLES 


DEGREES 
BRIX 

SPECIFIC  /  .  17-5\ 
GRAVITY  \    17.5/ 

DEGREES 
BAUME 

DEGREES 
BRIX 

SPECIFIC  /  ,  l"-5\ 
GRAVITY  \    17.57 

DEGREES 
BAUME" 

68.0 

1.33836 

37-11 

73.o 

1.36995 

39-64 

68.1 

1.33899 

37.16 

73.1 

1.37059 

39-69 

68.2 

1.33961 

37.21 

73-2 

1.37124 

39-74 

68.3 

1.34023 

37.26 

73-3 

I-37I88 

39-79 

68.4 

1.34085 

37.31 

73-4 

1.37252 

39.84 

68.5 

1.34148 

37-36 

73-5 

I-373I7 

39.89 

68.6 

1.34210 

3741 

73-6 

I-3738I 

39-94 

68.7 

1.34273 

37-47 

73-7 

1.37446 

39-99 

68.8 

1-34335 

37.52 

73-8 

I-375IO 

40.04 

68.9 

1.34398 

37-57 

73-9 

1-37575 

40.09 

69.0 

1.34460 

37-62 

74-o 

1.37639 

40.14 

69.1 

1.34523 

37-67 

74.1 

1.37704 

40.19 

69.2 

1.34585 

37-72 

74-2 

1.37768 

40.24 

69.3 

1.34648 

37-77 

74-3 

1-37833 

40.29 

60.4 

1-347" 

37.82 

74-4 

1.37898 

40.34 

69.5 

1.34774 

37.87 

74-5 

1.37962 

40.39 

69.6 

1.34836 

37.92 

74-6 

1.38027 

40.44 

69.7 

1.34899 

37-97 

74-7 

1.38092 

40.49 

69.8 

1.34962 

38.02 

74-8 

1-38157 

40.54 

69.9 

1-35025 

38.07 

74-9 

1.38222 

40.59 

70.0 

1.35088 

38.12 

75-o 

1.38287 

40.64 

70.1 

I-35I5I 

38.18 

75-i 

1.38352 

40.69 

70.2 

L352I4 

38.23 

75-2 

1.38417 

40.74 

70-3 

I.35277 

38.28 

75-3 

1.38482 

40.79 

70.4 

1  -35340 

38.33 

75-4 

I.38547 

40.84 

70-5 

1.35403 

38.38 

75-5 

1.38612 

40.89 

70.6 

1.35466 

38.43 

75-6 

1.38677 

40.94 

70.7 

1-35530 

38-48 

75-7 

L38743 

40.99 

70.8 

1.35593 

38.53 

75-8 

1.38808 

41.04 

70.9 

1.35656 

38.58 

75-9 

1.38873 

41.09 

71.0 

1.35720 

38-63 

76.0 

1.38939 

41.14 

71.1 

i'35783 

38.68 

76.1 

1.39004 

41.19 

71.2 

1.35847 

38.73 

76.2 

1.39070 

41.24 

71.3 

i.359io 

38.78 

76.3 

L39I35 

41.29 

71.4 
71-5 

1-35974 
1.36037 

38-83 
38.88 

76.4 
76.5 

1.39201 
1.39266 

41-33 
41.38 

71.6 

1.36101 

38.93 

76.6 

1.39332 

4*-43 

71.7 

1.36164 

38.98 

76.7 

1-39397 

41.48 

71.8 

1.36228 

39-03 

76.8 

1.39463 

4L53 

71.9 

1.36292 

39-o8 

76.9 

1.39529 

41.58 

72.0 

1.36355 

39-13 

77-0 

1-39595 

41.63 

72.1 

1.36419 

39-19 

77.1 

1.39660 

41.68 

72.2 

1.36483 

39-24 

77-2 

1.39726 

41-73 

72-3 

1.36547 

39-29 

77-3 

1.39792 

41.78 

72.4 

1.36611 

39-34 

77-4 

1.39858 

41.83 

72-5 

1.36675 

39-39 

77-5 

1.39924 

41.88 

72.6 

1.36739 

39-44 

77-6 

1.39990 

41-93 

72.7 

1.36803 

39-49 

77-7 

1.40056 

41.98 

72.8 

1.36867 

39-54 

77.8 

1.40122 

42.03 

72.9 

1.36931 

39-59 

77«9 

i  40188 

42.08 

TABLES 


293 


DEGREES 
BRIX 

SPECIFIC  /  ,  1^\ 
GRAVITY  \    17.5/ 

DEGREES 
BAUME 

DEGREES 
BRIX 

SPECIFIC  /  ,  17.5\ 
GRAVITY  \    17.57 

DEGREES 
BAUME 

78.0 

1.40254 

42.13 

83.0 

1.43614 

44.58 

78.1 

1.40321 

42.18 

83.1 

1.43682 

44.62 

78.2 

1.40387 

42.23 

83-2 

1.43750 

44.67 

78.3 

L404S3 

42.28 

83.3 

I.438I9 

44.72 

78.4 

1.40520 

42.32 

834 

1.43887 

44-77 

78.5 

1.40586 

42.37 

83.5 

1-43955 

44.82 

78.6 

1.40652 

42.42 

83.6 

1.44024 

44.87 

78.7 

1.40719 

42.47 

83.7 

1.44092 

44.91 

78.8 

1.40785 

42.52 

83.8 

1.44161 

44.96 

78.9 

1.40852 

42-57 

83.9 

1.44229 

45.01 

79.0 

1.40918 

42.62 

84.0 

1.44298 

45.06 

79.1 

1.40985 

42.67 

84.1 

1.44367 

45.ii 

79.2 

1.41052 

42.72 

84.2 

1.44435 

45.16 

79-3 

1.41118 

42.77 

84.3 

1.44504 

45.21 

79-4 

1.41185 

42.82 

84.4 

1-44573 

45.25 

79-5 

1.41252 

42.87 

84.5 

1.44641 

45-30 

79.6 

1.41318 

42.92 

84.6 

1.44710 

45-35 

79-7 

I.4I385 

42.96 

84-7 

1.44779 

4540 

79-8 

1.41452 

43.01 

84.8 

1.44848 

4545 

79-9 

1.41519 

43.06 

84.9 

1.44917 

45-49 

80.0 

1.41586 

43-11 

85.0 

1.44986 

45-54 

80.  i 

1-41653 

43.16 

85.1 

145055 

45-59 

80.2 

1.41720 

43.21 

85.2 

1.45124 

45-64 

80.3 

1.41787 

43.26 

85-3 

I.45I93 

45.69 

80.4 

1.41854 

43.31 

85.4 

1.45262 

45.74 

80.5 

1.41921 

43.36 

85.5 

L4533I 

45.78 

80.6 

1.41989 

43-41 

85.6 

1.45401 

45.83 

80.7 

1.42056 

43-45 

85.7 

1.45470 

45-88 

80.8 

1.42123 

43-50 

85-8 

1.45539 

45-93 

80.9 

1.42190 

43-55 

85-9 

1.45609 

45-98 

81.0 

1.42258 

43.6o 

86.0 

1.45678 

46.02 

81.1 

1.42325 

43.65 

86.1 

1.45748 

46.07 

81.2 

1.42393 

43-70 

86.2 

1.45817 

46.12 

81.3 

1.42460 

43-75 

86.3 

1.45887 

46.17 

81.4 

1.42528 

43.80 

86.4 

L45956 

46.22 

81.5 

1.42595 

43.85 

86.5 

1.46026 

46.26 

81.6 

1.42663 

43.89 

86.6 

1.46095 

46.31 

81.7 

1.42731 

43-94 

86.7 

1.46165 

46.36 

81.8 

1.42798 

43-99 

86.8 

1.46235 

46.41 

81.9 

1.42866 

44.04 

86.9 

1  .46304 

46.46 

82.0 

1.42934 

44.09 

87.0 

1.46374 

46.50 

82.1 

1.43002 

44.14 

87.1 

1.46444 

46.55 

82.2 

1.43070 

44.19 

87.2 

1.46514 

46.60 

82.3 

L43I37 

44.24 

87-3 

1.46584 

46.65 

82.4 

1.43205 

44.28 

87.4 

1.46654 

46.69 

82.5 

L43273 

44.33 

87.5 

1.46724 

46.74 

82.6 

L4334I 

44.38 

87.6 

1.46794 

46.79 

82.7 

1.43409 

44-43 

87.7 

1.46864 

46.84 

82.8 

1.43478 

44.48 

87.8 

1.46934 

46.88 

82.9 

I-43546 

44-53 

87.9 

1.47004 

46.93 

294 


TABLES 


DEGREES 
BRIX 

SPECIFIC  /  .  17.5\ 
GRAVITY  \a  17.5/ 

DEGREES 
BAUME 

DEGREES 
BRIX 

SPECIFIC  /  »  17.5\ 
GRAVITY  \a  17.5/ 

DEGREES 
BAUME 

88.0 

1.47074 

46.98 

93.0 

L50635 

49-34 

88.1 

I-47I45 

47.03 

93-1 

1.50707 

49-39 

88.2 

I.472I5 

47.08 

93.2 

1.50779 

49-43 

88.3 

1.47285 

47.12 

93-3 

1.50852 

4948 

88.4 

I.47356 

47-  17 

93-4 

1.50924 

49-53 

88.5 

1.47426 

47.22 

93-5 

1.50996 

49-57 

88.6 

1.47496 

47.27 

93-6 

1.51069 

49.62 

88.7 

1.47567 

47.31 

93-7 

1.51141 

49.67 

88.8 

1.47637 

47-36 

93-8 

1.51214 

49.71 

88.9 

1.47708 

47.41 

93-9 

1.51286 

49.76 

89.0 

1.47778 

47.46 

94.0 

L5I359 

49.81 

89.i 

1.47849 

47-50 

94.1 

L5I43I 

49.85 

89.2 

1.47920 

47-55 

94.2 

I-5I5°4 

49.90 

89.3 

1.47991 

47.60 

94-3 

L5I577 

49.94 

89.4 

1.48061 

47.65 

94-4 

1.51649 

49-99 

89-5 

1.48132 

47.69 

94-5 

1.51722 

50.04 

89.6 

1.48203 

47-74 

94.6 

I.5I795 

50.08 

89.7 

1.48274 

47-79 

94-7 

1.51868 

S0-^ 

89.8 

1.48345 

47.83 

94-8 

1.51941 

50.18 

89.9 

1.48416 

47.88 

94-9 

1.52014 

50.22 

90.0 

1.48486 

47-93 

95-o 

1.52087 

50.27 

90.1 

1.48558 

47.98 

95-1 

1.52159 

50.32 

90.2 

1.48629 

48.02 

95-2 

1.52232 

50.36 

90.3 

1.48700 

48.07 

95-3 

1.52304 

50.41 

90.4 

1.48771 

48.12 

95-4 

1.52376 

50.45 

90.S 

1.48842 

48.17 

95-5 

1.52449 

50.50 

90.6 

1.48913 

48.21 

95-6 

1.52521 

50.55 

90.7 

1.48985 

48.26 

95-7 

1.52593 

50.59 

90.8 

1.49056 

48.31 

95-8 

1.52665 

50.64 

90.9 

1.49127 

48.35 

95-9 

1.52738 

50.69 

91.0 

1.49199 

48.40 

96.0 

1.52810 

50.73 

91.1 

1.49270 

48.45 

96.1 

1.52884 

50.78 

91.2 

1.49342 

48.50 

96.2 

1.52958 

50.82 

91-3 

1.49413 

48.54 

96.3 

1-53032 

50.87 

91.4 

1.49485 

48.59 

96-4 

1.53106 

50.92 

91-5 

I.49556 

48.64 

96.5 

1.53180 

50.96 

91.6 

i  .49628 

48.68 

96.6 

1.53254 

51.01 

91.7 

1.49700 

48.73 

96.7 

I.53328 

5L05 

91.8 

1.49771 

48.78 

96.8 

1.53402 

51.10 

91.9 

1-49843 

48.82 

96-9 

1.53476 

5LI5 

92.0 

1.49915 

48.87 

97.0 

1.53550 

5LI9 

92.1 

1.49987 

48.92 

97.1 

1.53624 

51.24 

92.2 

1.50058 

48.96 

97-2 

1.53698 

51.28 

92.3 

1.50130 

49,01 

97-3 

1.53772 

Si-33 

92.4 

1.50202 

49.06 

97-4 

1.53846 

S1^8 

92.5 

1.50274 

49.11 

97-5 

1.53920 

51.42 

92.6 

1.50346 

49.15 

97.6 

1-53994 

51.47 

92.7 

1.50419 

49.20 

97-7 

1.54068 

5I-51 

92.8 

1.50491 

49-25 

97-8 

1.54142 

51.56 

92.9 

1-50563 

49.29 

97-9 

1.54216 

51.60 

TABLES 


295 


DEGREES 
BRIX 

SPECIFIC  /  ,  17.5\ 
GRAVITY  \a  17.5/ 

DEGREES 
BAUME 

DEGREES 
BRIX 

SPECIFIC  /  ,  17.5\ 
GRAVITY  \a  17.57 

DEGREES 
BAUM£ 

98.0 

1.54290 

5L65 

99-0 

1.55040 

52.11 

98.1 

1.54365 

5I-70 

99.1 

i.55"5 

52.15 

98.2 

1.54440 

51-74 

99.2 

I.55I89 

52.20 

98.3 

I.545I5 

5J-79 

99-3 

1.55264 

52.24 

98.4 

1.54590 

51-83 

99-4 

1.55338 

52.29 

98.5 

1.54665 

51.88 

99-5 

I-554I3 

52.33 

98.6 

1.54740 

51.92 

99.6 

1.55487 

52.38 

98.7 

I-548I5 

5J-97 

99-7 

1.55562 

52.42 

98.8 

1.54890 

52.01 

99.8 

1-55636 

52.47 

98.9 

I-54965 

52.06 

99.9 

I-557II 

52.51 

100.  0 

1.55785 

52.56 

2.  — STAMMER'S  TABLE   OF  TEMPERATURE  CORRECTIONS  FOR 
BRIX   HYDROMETER   READINGS1    {For  mercurial  thermometer) 


DEGREE  BRIX  OF  THE  SOLUTION 

DEGREE 

CENTI- 

0 

5 

10 

15 

20 

25 

30 

35 

40 

50 

60 

70 

75 

GRADE 

The  degree  read  is  to  be  decreased  by  — 

0 

0.17 

0.30 

0.41 

0.52 

0.62 

0.72 

0.82 

0.92 

0.98 

i.  ii 

1.22 

1.25 

1.29 

5 

0.23 

0.30 

0-37 

0.44 

0.52 

o.59 

0.65 

0.72 

0-75 

0.80 

0.88 

0.91 

0.94 

10 

O.2O 

0.26 

0.29 

o.33 

0.36 

0-39 

0.42 

o-45 

0.48 

0.50 

0-54 

0.58 

0.61 

ii 

0.18 

0.23 

0.26 

0.28 

0.31 

0-34 

0.36 

o.39 

0.41 

0.43 

o-47 

0.50 

°-53 

12 

0.16 

0.20 

0.22 

0.24 

0.26 

0.29 

0.31 

0-33 

0-34 

0.36 

0.40 

0.42 

0.46 

13 

0.14 

0.18 

0.19 

0.21 

O.22 

0.24 

0.26 

0.27 

0.28 

0.29 

o.33 

0-35 

o.39 

14 

0.12 

0.15 

0.16 

O.I7 

0.18 

0.19 

O.2I 

O.22 

0.22 

0.23 

0.26 

0.28 

0.32 

15 

0.09 

O.II 

0  12 

0.14 

O.I4 

0.15 

0.16 

0.17 

0.16 

0.17 

0.19 

0.21 

0.25 

16 

0.06 

0.07 

0.08 

O.09 

0.10 

O.IO 

O.II 

O.I2 

O.I2 

0.12 

0.14 

0.16 

0.18 

17 

0.02 

O.02 

0.03 

0.03 

0.03 

0.04 

0.04 

0.04 

0.04 

0.04 

0.05 

0.05 

0.06 

The  degree  read  is  to  be  increased  by  — 

18 

0.02 

0.03 

0.03 

0.03 

0.03 

0.03 

0.03 

0.03 

O.O3 

0.03 

0.03 

0.03 

O.O2 

19 

0.06 

0.08 

0.08 

0.09 

0.09 

O.IO 

O.IO 

O.IO 

O.IO 

O.IO 

O.IO 

0.08 

0.06 

20 

O.II 

0.14 

0.15 

0.17 

0.17 

0.18 

0.18 

0.18 

0.19 

0.19 

0.18 

0.15 

O.II 

21 

O.l6 

0.20 

0.22 

0.24 

0.24 

0.25 

0.25 

0.25 

0.26 

0.26 

0.25 

0.22 

0.18 

22 

0.21 

0.26 

O.29 

0.31 

0.31 

0.32 

0.32 

0.32 

0.33 

0.34 

0.32 

0.29 

0.25 

23 

0.27 

0.32 

0-35 

0-37 

0.38 

0-39 

o.39 

0.39 

0.40 

0.42 

0-39 

0.36 

°-33 

24 

0.32 

0.38 

0.41 

0-43 

0.44 

0.46 

0.46 

0.47 

0.47 

0.50 

0.46 

0-43 

0.49 

25 

0-37 

o-44 

0.47 

0.49 

0.51 

0-53 

0-54 

0.55 

0.55 

0.58 

0-54 

0.51 

0.48 

26 

0-43 

0.50 

o-54 

0.56 

0.58 

0.60 

0.61 

0.62 

0.62 

0.66 

0.62 

0.58 

o.55 

27 

0.49 

0-57 

0.61 

0.63 

0.65 

0.68 

0.68 

0.69 

0.70 

0.74 

0.70 

0.65 

0.62 

28 

0.56 

0.64 

0.68 

0.70 

0.72 

0.76 

0.76 

0.78 

0.78 

0.82 

0.78 

0.72 

0.70 

29 

0.63 

0.71 

0-75 

0.78 

0.79 

0.84 

0.84 

0.86 

0.86 

0.90 

0.86 

0.80 

0.78 

30 

0.70 

0.78 

0.82 

0.87 

0.87 

0.92 

0.92 

0.94 

0.94 

0.98 

0.94 

0.88 

0.86 

35 

1.  10 

1.17 

1.22 

1.24 

1.30 

1.32 

1-33 

1-35 

1.36 

i-39 

!-34 

1.27 

1.25 

40 

1.50 

1.61 

1.67 

I.7I 

1-73 

1.79 

1.79 

1.80 

1.82 

1-83 

1.78 

1.69 

1.65 

5o 

2.65 

2.7I 

2-74 

2.78 

2.80 

2.80 

2.80 

2.80 

2.79 

2.70 

2.56 

2.51 

60 

3-87 

3.88 

3.88 

3-88 

3-88 

3.88 

3.88 

3-90 

3-82 

3-70 

3-43 

3-4i 

70 

5-18 

5-20 

5-14 

5-13 

^.10 

5-08 

5-o6 

4.90 

4.72 

4-47 

4-35 

80 

6.62 

6.59 

6-54 

6.46 

6.38 

6.30 

6.26 

6.06 

5-82 

5.50 

5-33 

1  Note  that  these  corrections  take  into  consideration  that  the  glass  of  the  hydrometer  as 
well  as  the  sugar  solution  itself  is  affected  by  the  temperature  change. 


296 


TABLES 


3.  — SCHMITZ'S  TABLE  FOR  DETERMINING  PERCENTAGE  OF 

BRIX   READINGS 

(N  =  26.048  grams ;  allowance  being  made  for  an  increase 


BRIX  READING 

BRIX  READING  AND 

FROM   0.5   TO    12.0 

SACCHARI- 

METRIC 

0  5 

1.0 

1  5 

2.0 

2.5 

3.0 

3.5 

4  0 

A    K 

Tenths  of 
a  Division 

Per  cent 
Sucrose 

DIVISIONS 

1.0019 

1.0039 

1.0058 

1.0078 

1.0098 

1.0117 

1.0137 

1.0157 

4.O 

I.OI77 

O.I 

0.03 

i 

0.29 

0.29 

0.29 

0.28 

0.28 

0.28 

0.28 

0.28 

0.28 

0.2 

0.06 

2 

o-57 

o-57 

°-57 

o-57 

0.56 

0.56 

0.56 

0.56 

0-3 

0.08 

3 

0.85 

0.85 

0.85 

0.85 

0.85 

0.85 

0.84 

0.84 

0.4 

0-5 

O.I  I 

0.14 

4 

1.42 

1.42 

1.41 

1.41 

1.41 

1.41 

1.40 

0.6 

0.17 

6 

1.70 

1.70 

1.69 

1.69 

1.69 

1.68 

0.7 

0.19 

7 

1.98 

1.98 

1.98 

1.97 

1.97 

1.96 

0.8 

0.22 

8 

2.26 

2.26 

2.26 

2.25 

2.25 

0.9 

0.25 

9 

2-54 

2-54 

2-53 

2-53 

10 

2.82 

2.82 

2.81 

2.81 

ii 

3-10 

3-09 

3-09 

12 
13    ' 

3.38 

3-38 
3-66 

3-37 
3-65 

14 

3-94 

3-93 

BRIX  READING 

FROM    12.5  TO   20.0 

15 

16 

4.21 
4-49 

Tenths  of 

Per  cent 

18 

a  Division 

Sucrose 

19 

20 

O.I 

0.03 

21 

O.2 
0-3 

0.05 
0.08 

22 
23 

0.4 

O.II 

24 

0.6 

0.13 
0.16 

a 

0.7 

0.19 

27 

0.8 

0.21 

28 

0.9 

O.24 

29 

30 

31 

32 

33 

34 

35 

36 

37 

38 

39 

TABLES 


297 


SUGAR  SOLUTIONS  WHEN  THE  SACCHARIMETRIC  AND 
ARE  KNOWN 

of  one  tenth  in  volume  in  clarifying  for  polarizing.) 


CORRESPONDING  SPECIFIC  GRAVITY 

SACCHARI- 

5.0 

5.5 

6.0 

6.5 

7.0 

7.5 

8.0 

8.5 

9.0 

9.5 

10.0 

METRIC 

1.0197 

1.0217 

1.0237 

1.0258 

1.0278 

1.0298 

1.0319 

1-0339 

1.0360 

1.0381 

1.0401 

DIVISIONS 

0.28 

0.28 

0.28 

0.28 

0.28 

0.28 

0.28 

0.28 

0.28 

0.28 

0.28 

i 

0.56 

0.56 

0.56 

0.56 

0.56 

0-55 

0.55 

0-55 

0-55 

0-55 

o.55 

2 

0.84 

0.84 

0.84 

0.84 

0.83 

0.83 

0.83 

0.83 

0.83 

0.83 

0.82 

3 

1.  12 

1.  12 

1.  12 

i.  II 

I.  II 

i.  ii 

i.  ii 

i.  ii 

I.IO 

I.IO 

I.IO 

4 

I.4O 

1.68 

I.4O 

1.68 

1.40 
1.67 

1-39 
1.67 

1-39 

1.67 

1-39 
1.66 

It 

1.38 
1.66 

1.38 

1.66 

1.38 
1.65 

1.37 
1.65 

6 

1.96 

1.96 

1-95 

1-95 

1.95 

1.94 

1.94 

1-93 

i-93 

1-93 

1.92 

7 

2.24 

2.24 

2.23 

2.23 

2.22 

2.22 

2.22 

2.21 

2.21 

2.20 

2.  2O 

8 

2.52 

2.52 

2.51 

2-51 

2.50 

2.50 

2.49 

2.49 

2.48 

2.48 

2.47 

9 

2.80 

2.80 

2.79 

2.79 

2.78 

2.78 

2.77 

2.76 

2.76 

2-75 

2-75 

10 

3.08 

3.08 

3-07 

3.06 

3-06 

3-05 

3-05 

3-04 

3-03 

3.03 

3.02 

ii 

3.36 

3-35 

3-34 

3-34 

3-33 

3-32 

3.32 

3-31 

3-30 

3-30 

12 

3.64 

3-64 

3.62 

3-61 

3.61 

3.60 

3-59 

3-59 

3-58 

3-57 

13 

3-92 

3-92 

3-9i 

3-90 

3.89 

3-88 

3-88 

3.87 

3-86 

3-85 

3.85 

14 

4.20 

4.19 

4.19 

4.18 

4.17 

4.16 

4-15 

4-15 

4.14 

4.13 

4.12 

15 

4.48 

4-47 

447 

4.46 

445 

4.44 

443 

442 

4.41 

4.40 

4.40 

10 

4-77 

4.76 

4-75 

4-74 

4-73 

4.72 

4.71 

4.70 

4.69 

4.68 

4.67 

17 

5-03 

5-02 

5.01 

5.00 

4-99 

4.99 

4-97 

4-97 

4.96 

4-95 

18 

5-32 

5-31 

5-29 

5-28 

5-27 

5-26 

5-25 

5-24 

5.23 

5.22 

19 

5-58 

5-57 

5.56 

5-55 

5-54 

5-53 

5-52 

5.51 

5.50 

20 

5-86 

5-85 

5.84 

5-83 

5.82 

5.81 

5-79 

5-77 

21 

6.13 

6.12 

6.09 

6.08 

6.07 

6^06 

6.05 

22 

6.41 

6.40 

6^38 

6-37 

6.36 

6-35 

6-33 

6.32 

23 

6.67 

6.66 

6.65 

6.64 

6.62 

6.61 

6.60 

24 

6.94 

6-93 

6.91 

6.90 

6.89 

6.87 

25 

7.22 

7.20 

7.19 

7.17 

7.16 

7-15 

26 

7.48 

7.46 

745 

744 

742 

27 

7.76 

7-74 

7-73 

7.71 

7.70 

28 

8.02 

8.00 

7-99 

7-97 

29 

8.28 

8.26 

8.25 

3° 

8.55 

8-54 

8.52 

8.83 

8.81 

8.80 

32 

9.09 

9.07 

33 

9-35 

34 

9.62 

35 

37 

38 

39 

298 


TABLES 


BRIX  READING 

BRIX  READING  AND 

FROM   0.5   TO    12.0 

SACCHARI- 

1 

METRIC 

10.5 

11.0 

11.5 

12.0 

12.5 

13.0 

13.5 

14.0 

14.5 

Tenths  of 
a  Division 

Per  cent 

Sucrose 

DIVISIONS 

1.0422 

1.0443 

1.0464 

1.0485 

1.0506 

1.0528 

1.0549 

1.0570 

1.0592 

O.I 

0.03 

i 

0.28 

0.27 

0.27 

0.27 

0.27 

0.27 

0.27 

0.27 

0.27 

0.2 

0.06 

2 

0-55 

0-55 

0-55 

o-55 

o-54 

o-54 

o-54 

o-54 

0-54 

°-3 

0.08 

3 

0.82 

0.82 

0.82 

0.82 

0.82 

0.8  1 

0.81 

0.81 

0.81 

0.4 

O.II 

4 

1.  10 

1.  10 

1.09 

1.09 

1.09 

1.09 

i.  08 

i.  08 

i.  08 

°-5 

0.14 

5 

1-37 

i-37 

1.36 

1.36 

1.36 

1.36 

i-35 

J-35 

1-35 

0.6 

0.17 

6 

1.64 

1.64 

1.64 

1.64 

1.63 

1.63 

1.62 

1.62 

1.62 

0.7 

0.19 

7 

1.92 

1.91 

1.91 

1.91 

1.90 

1.90 

1.89 

1.89 

1.89 

0.8 

0.22 

8 

2.19 

2.19 

2.18 

2.18 

2.18 

2.17 

2.17 

2.16 

2.16 

0.9 

O.25 

9 

2.47 

2.46 

2.46 

2-45 

245 

2.44 

2.44 

243 

243 

10 

2.74 

2.74 

2-73 

2.73 

2.72 

2.71 

2.71 

2.70 

2.70 

ii 

3.02 

3.01 

3.00 

3.00 

2.99 

2.99 

2.98 

2-97 

2-97 

12 

3-29 

3.28 

3-28 

3-27 

3-26 

3.26 

3-25 

3-24 

3-24 

13 

3.56 

3.56 

3-55 

3-54 

3-54 

3-53 

3-52 

3-51 

3.51 

14 

3.84 

3-83 

3.82 

3-82 

3.81 

3.80 

3-79 

3.78 

3.78 

BRIX  READING 

15 

16 

4.11 
4-39 

4.11 
4.38 

4.10 
4-37 

4.09 
4-3° 

4.08 
4-35 

4.07 
4-34 

4.06 
4-33 

4.06 
4-33 

4-05 
4-32 

FROM  12.5  TO  20.0 

i? 

4.66 

4.65     4.64 

4-63 

4.62 

4.62 

4.61 

4.60 

Tenths  of 
a  Division 

Per  cent 
Sucrose 

18 
19 

4-93 
5-21 

4-93 

5-20 

4.91 
5-19 

4.91 
5-i8 

4.90 
5-17 

4.89 
5.16 

4.88 
5-15 

4.87 
5-14 

5.13 

20 

549 

5-47 

546 

545 

5-44 

543 

542 

54i 

540 

O.I 

0.03 

21 

5.76 

5-75 

5-74 

5-73 

5-71 

5-70 

5.69 

5.68 

5.67 

O.2 

0.05 

22 

6.03 

6.02 

6.01 

6.00 

5-99 

5-97 

5-90 

5-95 

5-94 

°-3 

0.08 

23 

6.31 

6.30 

6.28 

6.27 

6.26 

6.24 

6.23 

6.22 

6.21 

0.4 

O.II 

24 

6.58 

6.57 

6.56 

6-54 

6-53 

6.52 

6.50 

6.49 

6.48 

0.5 

0.13 

25 

6.86 

6.84 

6.83 

6.82 

6.80 

6.79 

6.78 

6.76 

6-75 

0.6 

0.16 

26 

7-13 

7.12 

7.10 

7.09 

7.07 

7.06 

7.05 

7-03 

7.02 

0.7 

0.19 

27 

7.41 

7-39 

7.38 

7.36 

7-35 

7-33 

7-32 

7-30 

7.29 

0.8 

0.21 

28 

7.68 

7.66 

7.65 

7-63 

7.62 

7.60 

7-59 

7-57 

7-56 

0.9 

0.24 

29 

7.96 

7-94 

7.92 

7.91 

7.89 

7.87 

7.86 

7.84 

7.83 

3° 

8.23 

8.21 

8.20 

8.18 

8.16 

8.15 

8.13 

8.ii 

8.10 

31 

8.50 

8.49 

8.47 

8.45 

8.44 

8.42 

8.40 

8-39 

8-37 

32 

8.78 

8.76 

8.74 

8.73 

8.71 

8.69 

8.67 

8.66 

8.64 

33 

9.05 

9-03 

9.02 

9.00 

8.98 

8.96 

8.94 

8-93 

8.91 

34 

9-33 

9.3i 

9.29 

9.27 

9-25 

9-23 

9.22 

9.20 

9.18 

35 

9.60 

9.58 

9.56 

9-54 

9-53 

9-51 

949 

947 

945 

36 

9.88 

9.86 

9.84 

982 

9.80 

978 

9.76 

9-74 

9.72 

37 

10.15 

10.13 

10.  1  1 

10.09 

10.07 

10.05 

10.03 

IO.OI 

9.99 

38 

10.40 

10.38 

10.36 

10.34 

10.32 

10.30 

10.28 

10.26 

39 

10.68 

10.66 

10.64 

10.61 

10.59 

10.57 

iQ-55 

10.53 

TABLES 


299 


CORRESPONDING  SPECIFIC  GRAVITY 

15.0 

15.5 

16.0 

16.5 

17.0 

17.5 

18.0 

18.5 

19.0 

19.5 

20.0 

SACCHARI- 

METRIC 

1.0613 

1.0635 

1.0657 

1.0678 

1.0700 

1.0722 

1.0744 

1.0766 

1.0788 

1.081  1 

1.0833 

0.27 

0.27 

0.27 

0.27 

0.27 

0.27 

0.27 

0.27 

0.27 

0.27 

0.26 

I 

0.54 
0.81 

0-54 
0.81 

0-54 
0.80 

o-54 
0.80 

0-53 
0.80 

o-53 
0.80 

0-53 
0.80 

o-53 
0.80 

0.79 

o-53 
0.79 

0-53 
0.79 

2 

3 

1.  08 

i.  08 

1.07 

1.07 

1.07 

1.07 

i.  06 

i.  06 

1.  06 

1.06 

1.  06 

4 

I-35 

1-34 

1-34 

!.34 

!.34 

i-33 

i-33 

1-33 

1.32 

1.32 

1.32 

5 

1^62 

1.61 

1.61 

1.61 

1.  60 

i.  60 

1.60 

i-59 

i-59 

1.58 

6 

1.88 

1.88 

1.88 

1.87 

1.87 

1.86 

1.86 

1.86 

1.1s 

1.85 

1.85 

7 

2.15 

2.15 

2.15 

2.14 

2.14 

2.13 

2.13 

2.12 

2.12 

2.12 

2.  II 

8 

2.42 

2.42 

2.41 

2.41 

2.40 

2.40 

2-39 

2-39 

2.38 

2.38 

2-37 

9 

2.69 

2.69 

2.68 

2.68 

2.67 

2.67 

2.66 

2.65 

2.65 

2.64 

2.64 

10 

2.96 

2-95 

2-95 

2.94 

2.94 

2.93 

2.92 

2.92 

2.91 

2.91 

2.90 

ii 

3-23 

3.22 

3.22     3.21 

3.20 

3.20 

3-19 

3.18 

3-18 

3-17 

3-17 

12 

3-50 

3-49 

3-49 

348 

3-47 

346 

3-45 

3-44 

3-44 

3-43 

13 

3-77 

3-75 

3-75 

3-74 

3-73 

3-72 

3-72 

3-70 

3-69 

4.04 

4.03 

4.02 

4.02 

4.01 

4.00 

3-99 

3.98 

3-97 

3-97 

3.96 

15 

4-30 

4.29 

4.28 

4.27 

4.26 

4.26 

4-25 

4.24 

4-23 

4.22 

16 

4.58 

4-57 

4-56 

4-55 

4-54 

4-53 

4-52 

4-51 

4-50 

4.49 

4.48 

17 

4-85 

4.84 

4-83 

4.82 

4.81 

4.80 

4-79 

4.78 

4-77 

4.76 

4-75 

18 

5.12 

5-II 

5.10 

5.09 

5.08 

5.06 

5-05 

5-04 

5-03 

5.02 

5.01 

19 

5-39 

5.38 

5.36 

5-35 

5-34 

5-33 

5-32 

53i 

5-30 

5-29 

5.28 

20 

5-66 

5.65 

5.63 

5.62 

5.61 

5.60 

5-59 

5*58 

5.56 

5-55 

5-54 

21 

5-93 

5-9° 

5.88 

5-87 

5-85 

5-84 

5-83 

5-82 

5.80 

22 

6.  20 

6!i8 

6.17 

6.16 

6.14 

6.13 

6.12 

6.09 

6.08 

6.07 

23 

6.46 

6-45 

6.44 

6-43 

6.41 

6.40 

6-39 

6-37 

6.36 

6-35 

6-33 

24 

6-73 

6.72 

6.71 

6.69 

6.68 

6.67 

6.65 

6.64 

6.63 

6.61 

6.60 

25 

7.00 

6.99 

6.97 

6.96 

6-95 

6-93 

6.92 

6.90 

6.89 

6.88 

6.86 

26 

7.27 

7.26 

7.24 

7-23 

7.21 

7.20 

7.18 

7.17 

7.15 

7.14 

7-13 

27 

7-54 

7-53 

7.51 

7-50 

7.48 

7-47 

7-45 

7-44 

7.42 

7.40 

7-39 

28 

7.81 

7.80 

7.78 

7-77 

7-75 

7-73 

7.72 

7.70 

7.68 

7.67 

7.65 

29 

8.08 

8.06 

8.05 

8.03 

8.02 

8.00 

7.98 

7-97 

7-95 

7-93 

7.92 

30 

8-35 

8-33 

8.32 

8.30 

8.28 

8.27 

8.25 

8.23 

8.21 

8.20 

8.18 

3l 

8.62 

8.60 

8.58 

8-57 

8-55 

8-53 

8.51 

8.50 

8.48 

8.46 

8-45 

32 

8.89 

8.87 

8.85 

8.84 

8.82 

8.80 

8.78 

8.76 

8-75 

8-73 

8.71 

33 

9.16 

9.14 

9.12 

9.10 

9.09 

9.07 

9-°5 

9-03 

9.01 

8.99 

8.97 

34 

9-43 

9.41 

9-39 

9-37 

9-35 

9-34 

9.3i 

9-3° 

9.28 

9.26 

9.24 

35 

9.70 

9.68 

9.66 

9.64 

9.62 

9.60 

9*58 

9-54 

9-52 

9-5° 

36 

9-97 

9-95 

9-93 

9.91 

9.89 

9.87 

9-85 

9.83 

9.81 

9-79 

9-77 

37 

10.24 

10.22 

10.20 

10.18 

10.15 

10.13 

IO.II 

10.09 

10.07 

10.05 

10.03 

38 

10.51 

10.49 

10.46 

10.44 

10.42 

10.40 

10.38 

10.36 

10.34 

10.32 

10.29 

39 

300 


TABLES 


BRIX  READING 

BRIX  READING  AND 

FROM    II.5   TO   22.5 

METRIC 

1  1  £ 

1  .  >  n 

1  •?  A 

1  O  E 

Tenths  of 
a  Division 

Per  cent 
Sucrose 

DIVISIONS 

1  l.O 

1.0464 

1Z.U 

1.0485 

1.0506 

lo.U 

1.0528 

lo.O 

1.0549 

1.0570 

40 

10.93 

10.91 

10.89 

10.86 

10.84 

10.82 

O.I 

0.03 

41 

II.I8 

ii.  16 

11.14 

II.  12 

11.09 

0.2 

0.05 

42 

11.46 

n-43 

11.41 

H-39 

11.36 

0-3 

0.08 

43 

11.71 

11.68 

u.66 

11.64 

0.4 

O.II 

44 

11.98 

11  -95 

H-93 

11.91 

o-5 
0.6 

0.13 
0.16 

45 
47 

12.25 

12.23 
12.50 

12.  2O 
12.47 

I2.I8 
12.45 

0.2 

0.19 

46 

12.74 

12.72 

0.8 

0.21 

48 

I3.O2 

12.99 

0.9 

0.24 

49 

13.26 

50 

52 

53 

54 

BRIX  READING 

55 
56 

FROM   23.0  TO   24.0 

Tenths  of 
a  Division 

Per  cent 
Sucrose 

58 
59 

60 

O.I 

0.03 

61 

0.2 

0.05 

62 

o-3 

O.o8 

63 

0.4 

O.IO 

64 

0.5 

0.13 

65 

0.6 

0.16 

66 

0.7 

0.18 

67 

0.8 

0.21 

68 

0.9 

0.23 

69 

70 

72 

73 

74 

P 

77 

78 

TABLES 


301 


CORRESPONDING  SPECIFIC  GRAVITY 

14.5 

15.0 

15.5 

16.0 

16.5 

17.0 

17.5 

SACCHARI- 

METRIC 

1.0592 

1.0613 

1.0635 

1.0657 

1.0678 

1.0700 

1.0722 

DIVISIONS 

10.80 

10.78 

10.76 

10.73 

10.71 

10.69 

10.67 

40 

11.07 

11-05 

11.03 

11.00 

10.98 

10.96 

10.94 

41 

n-34 

11.32 

11.29 

11.27 

11.25 

11.23 

ii.  20 

42 

II.OI 

11-59 

11.56 

n-54 

11.52 

11.49 

11.47 

43 

11.88 

u.86 

11.83 

11.81 

11.79 

11.76 

11.74 

44 

12.15 

12.13 

12.10 

12.08 

12.05 

12.03 

12.01 

45 

12.42 

12.40 

12.37 

12.35 

12.32 

12.30 

12.27 

46 

12.69 

12.67 

12.64 

12.  6l 

12.59 

12.56 

I2.54 

47 

12.97 

12.94 

12.91 

12.88 

12.86 

12.83 

I2.8I 

48 

13-23 

13.21 

13.18 

13.15 

13.13 

13.10 

13.07 

49 

I3-50 
I3-78 

13.48 
J3-75 

13-45 
13.72 

13-42 
13.69 

13.40 
13.66 

13-37 
13.64 

13-34 
I3.6I 

50 
5i 

14.02 

*3-99 

13.96 

13-93 

13.90 

13.88 

52 

14.29 

14.26 

14-23 

14.20 

14.17 

14.14 

53 

14.53 

14.50 

14.47 

14.44 

14.41 

54 

14.80 

14-77 

14.74 

14.71 

14.68 

55 

15-03 

15.00 

14.97 

14.94 

56 

15-30 

15-27 

15.24 

15.21 

57 

15-57 

15-54 

15-51 

I5.48 

58 

15.81 

I5-78 

15-75 

59 

16  05 

16.01 

60 

16.31 

16.28 

61 

16-55 

62 

16.82 

63 

64 

65 

66 

67 

68 

69 

70 

71 

72 

73 

74 

75 

76 

77 

78 

79 

80 

302 


TABLES 


BRIX  READING 

BRIX  READING  AND 

FROM    11.5  TO   22.5 

SACCHARI- 

Tenths  of 

Per  cent 

METRIC 

DIVISIONS 

18.0 

18.5 

19.0 

19.5 

20.0 

20.5 

a  Division 

Sucrose 

1.0744 

1.0766 

1.0788 

1.0811 

1.0833 

1.0855 

40 

10.64 

10.62 

10.  60 

10.58 

10.56 

10.54 

O.I 

0.03 

41 

10.91 

10.89 

10.87 

10.85 

10.82 

10.80 

0.2 

0.05 

42 

ii.  iB 

ii.  16 

11.13 

II.  II 

11.09 

11.07 

0.4 

0.08 

O.II 

43 
44 

H.45 
11.71 

11.42 
11.69 

11.40 

11.66 

11.38 
11.64 

11-35 
11.62 

"•59 

0-5 

0.13 

45 

11.98 

11.96 

"•93 

11.91 

11.88 

11.86 

0.6 

0.16 

46 

12.25 

12.22 

12.20 

12.17 

12.15 

12.12 

°-7 

0.19 

47 

12.51 

12.49 

12.46 

12.44 

12.41 

12.39 

0.8 

0  21 

48 

12.78 

12.75 

12.73 

12.70 

12.67 

12.65 

0.9 

0.24 

49 

13-05 

13.02 

12.99 

12.97 

12.94 

12.91 

50 

13.31 

13.29 

13.26 

13-23 

13.20 

13.18 

51 

I3-58 

13-55 

I3.52 

I3-50 

1347 

13.44 

52 

13.85 

13.82 

13.79 

13.76 

13.73 

13.70 

53 

14.11 

14.08 

14.05 

14.03 

14.00 

13.97 

54 

14.38 

14.35 

I4.32 

14.29 

14.26 

14.23 

BRIX  READING 

FROM    23.0  TO   24.0 

55 
56 

14.65 
14.91 

14.62 
14.88 

14.59 
14.85 

14.56 
14.82 

14-53 
14.79 

14.50 
14.76 

57 

15.18 

I5'I5 

15.12 

15.09 

15.06 

15.02 

Tenths  of 

Per  cent 

58 

15-45 

15.42 

15.38 

15-35 

15-32 

I5-29 

a  Division 

Sucrose 

59 

15.68 

15.65 

15.62 

15.58 

15-55 

60 

15.98 

15.95 

15.92 

15.88 

I5-85 

15.82 

O.I 

0.03 

61 

16.25 

16.21 

16.18 

16.15 

16.11 

16.08 

0.2 

0.05 

62 

16.52 

16.48 

16.45 

16.41 

16.38 

16.35 

0.3 

0.08 

63 

16.78 

16.75 

16.71 

16.68 

16.64 

16.61 

0.4 

0.10 

64 

17.05 

17.01 

16.98 

16.94 

16.91 

16.87 

0.5 

0.6 

0.13 
0.16 

§ 

17.32 

17.28 

17.55 

17.24 

17.21 
J7-47 

17.17 

17.44 

17.14 
17.40 

0.7 

0.18 

67 

17.81 

17.78 

17.74 

17.70 

17.67 

0.8 

O.2I 

68 

18.04 

18.00 

17.97 

17.93 

0.9 

o  23 

69 

18.31 

18.27 

18.23 

18.19 

70 

18.53 

18.50 

18.46 

18.76 

18.72 

72 

19.03 

18.99 

73 

19.25 

74 

19.52 

75 

• 

19.78 

76 

77 

78 

79 

80 

TABLES 


303 


CORRESPONDING  SPECIFIC  GRAVITY 

21.0 

21.5 

22.0 

22.5 

23.0 

23.5 

24.0 

SACCHARI- 

METRIC 

DIVISIONS 

1.0878 

i.ogoo 

1.0923 

1.0946 

1.0969 

1.0992 

1.1015 

10.52 

10.49 

10.47 

10.45 

10.43 

10.41 

10.38 

40 

10.78 

10.76 

10.74 

10.71 

10.69 

10.67 

10.65 

41 

11.04 

11.02 

11.00 

10.97 

10.95 

10.93 

10.90 

42 

H.3I 

11.28 

11.26 

11.24 

II.  21 

11.19 

11.17 

43 

11-57 

n-55 

11.52 

11.50 

11.47 

H.45 

11.42 

44 

11.83 

ii.  81 

11.78 

11.76 

H-73 

11.71 

11.69 

45 

12.09 

12.07 

12.05 

12.02 

12.00 

11.97 

11.94 

46 

12.36 

12.33 

12.31 

12.28 

12.26 

12.23 

12.21 

47 

12.62 

12.60 

12.57 

12.54 

12.52 

12.49 

12.47 

48 

12.88 

12.86 

12.83 

I2.8I 

12.78 

12-75 

12.73 

49 

13.15 

13.12 

13.09 

13.07 

13.04 

13.01 

12.99 

50 

1341 

13-39 

I3-36 

13-33 

I3-30 

13.27 

I3-25 

5i 

13.68 

13-65 

13.62 

13-59 

I3-56       |       13-53 

I3-5I 

52 

13-94 

^•Q1 

13.88 

I3-85 

13.82 

13-79 

13-77 

53 

14.20 

14.17 

14.14 

14.11 

14.08 

14.06 

14.02 

54 

14.47 

14.44 

14.41 

14.38 

14-35 

14.32 

14.29 

55 

14.73 

14.70 

14.67 

14.64 

I4.6I 

14.58 

z4-55 

56 

14.99 

14.96 

J4-93 

14.90 

I4.87 

14.84 

14.81 

57 

15.26 

15.23 

I5-I9 

I5.I6 

15.13 

15.10 

15-07 

58 

15.52 

15-49 

15.46 

1542 

15-39 

I5-36 

15-33 

59 

I5.78 

15-75 

I5-72 

15.69 

I5.65 

15.62 

15.59 

60 

16.05 

16.01 

15.98 

15-95 

J5-91 

15.88 

15-85 

61 

16.31 

16.28 

16.24 

16.21 

16.18 

16.14 

16.11 

62 

\6«57 

16.54 

16.51 

16.47 

16.44 

16.40 

16.37 

63 

16.84 

16.80 

16.77 

16.73 

16.70 

16.66 

16.63 

64 

17.10 

17.07 

17.03 

17.00 

16.96 

16.92 

16.89 

65 

17-37 

17-33 

17.29 

17.26 

17.22 

17.19 

I7-I5 

66 

17.63 

17.59 

17.56 

17.52 

17.48 

17-45 

17.41 

67 

17.89 

17.86 

17.82 

17.78 

17-74 

17.71 

17.67 

68 

18.16 

18.12 

18.08 

18.04 

18.00 

17.97 

17.93 

69 

18.42 

18.38 

18-35 

18.31 

18.27 

18.23 

18.19 

70 

18.68 

18.65 

18.61 

18.57. 

18.53 

18.49 

18.45 

71 

18.95 

18.91 

18.87 

18.83 

18.79 

18.75 

18.71 

72 

19.21 

19.17 

19-13 

19.09 

19.05 

19.01 

18.97 

73 

19.48 

19.44 

19.40 

19-35 

19-31 

19.27 

19.23 

74 

19.74 

19.70 

19.66 

19.62 

19-57 

19-53 

19.49 

75 

20.00 

19.96 

19.92 

19.88 

19.84 

19.80 

19-75 

76 

20.27 

20.22 

20.18 

20.14 

20.10 

20.06 

20.01 

77 

20.49 

20.45 

20.40 

20.36 

20.32 

20.27 

78 

20-75 

20.71 

20.66 

20.62 

20.58 

20.54 

79 

20.97 

20.93 

20.88 

20.84 

20.80 

80 

304 


TABLES 


4.  — EQUIVALENTS  OF  DEXTROSE,  MALTOSE,  AND  LACTOSE 
IN  PARTS  OF  COPPER  OXIDE  OBTAINED  BY  DEFREN'S 
METHOD  OF  DETERMINATION 


PARTS  COPPER 
OXIDE 

PARTS 
DEXTROSE 

PARTS 
MALTOSE 

PARTS 
LACTOSE 

PARTS  COPPER 
OXIDE 

PARTS 
DEXTROSE 

PARTS 
MALTOSE 

PARTS 
LACTOSE 

30 

13.2 

21.7 

18.8 

77 

34-0 

56.0 

48.5 

31 

13.7 

22.4 

19-5 

78 

344 

56.7 

49.2 

32 

14.1 

23.1 

20.1 

79 

34-9 

574 

49.8 

33 

14.6 

23-9 

20.7 

80 

354 

58.1 

50.5 

34 

15-0 

24.6 

21.4 

81 

35-9 

58.9 

35 

154 

25.3 

22.0 

82 

36'3 

59-6 

5J«7 

36 

26.1 

22.6 

83 

36.8 

60.3 

524 

37 

16.3 

26.8 

23-3 

84 

37-2 

61.1 

53-0 

38 

16.8 

27-5 

23.9 

85 

37-7 

61.8 

53-6 

39 

17.2 

28.3 

24.5 

86 

38.1 

62.5 

54-3 

40 

17.6 

29.0 

25.2 

87 

38.5 

63.3 

54-9 

41 

18.1 

29.7 

25-8 

88 

39-o 

64.0 

55-5 

42 

18.5 

30.5 

26.4 

89 

394 

64.7 

56.2 

43 

19.0 

31-2 

27.I 

90 

39-9 

65.5 

56.8 

44 

19.4 

31-9 

27.7 

91 

40.3 

66.2 

574 

45 

19.9 

32.7 

28.3 

92 

40.8 

66.9 

58.1 

46 

20.3 

334 

29.0 

93 

41.2 

67.7 

58.7 

47 

20.7 

34-1 

29.6 

94 

41.7 

68.4 

59-3 

48 

21.2 

34-8 

3O.2 

95 

42.1 

69.1 

60.0 

49 

21.6 

35-5 

30.8 

96 

42.5 

69.9 

60.6 

50 

22.1 

36-2 

3L5 

97 

43-° 

70.6 

61.2 

51 

22.5 

37-0 

32.1 

98 

434 

71.3 

61.9 

52 

23.0 

37-7 

32.7 

99 

43-9 

72.1 

62.5 

53 

234 

384 

33-3 

100 

444 

72.8 

63.2 

54 

23.8 

39-2 

34-0 

101 

44.8 

73-5 

63-8 

55 

24.2 

39-9 

34-6 

102 

45-3 

74-3 

64.4 

56 

24.7 

40.5 

35-2 

I03 

45-7 

75-0 

65-1 

57 
58 

25.1 

25'5 

41-3 
42.1 

Hi 

104 
105 

46.2 
46.6 

75-7 
76.5 

65-7 
66.3 

59 

26.0 

42.8 

37.1 

106 

47.0 

77.2 

67.0 

60 

26.4 

43-5 

37-8 

107 

47-5 

77-9 

67.6 

61 

26.9 

44-3 

384 

108 

48.0 

78.7 

68.2 

62 

27-3 

39-0 

109 

48.4 

794 

68.9 

63 

27.8 

45-7 

39-7 

no 

48.9 

80.1 

69.5 

64 

28.2 

46-5 

40.3 

in 

49-3 

80.9 

70.1 

65 

28.7 

47.2 

40.9 

112 

49-8 

81.6 

70.8 

66 

29.1 

47-9 

41.6 

"3 

50.2 

82.3 

71.4 

67 

29.5 

48.6 

42.2 

114 

50.7 

83-1 

72.0 

68 

30.0 

494 

42.8 

115 

83.8 

72.7 

69 

304 

50.1 

43-5 

116 

51*6 

84-5 

73-3 

70 

3°-9 

^0.8 

44.1 

117 

52.0 

85.2 

74.0 

71 

3^3 

51-6 

44-7 

118 

524 

85.9 

74.6 

72 

31-8 

52.3 

454 

119 

52.9 

86.6 

75-2 

73 

32.2 

53-0 

46.0 

120 

53-3 

87.4 

74 

32.6 

53-8 

46.6 

121 

53-8 

88.1 

76.6 

75 

33-1 

54-5 

47-3 

122 

54-2 

88.9 

77.2 

76 

33-5 

55-2 

47-9 

123                54-7 

89.6 

77-9 

TABLES 


305 


PARTS  COPPER 
OXIDE 

PARTS 
DEXTROSE 

PARTS 
MALTOSE 

PARTS 
LACTOSE 

PARTS  COPPER 
OXIDE 

PARTS 
DEXTROSE 

PARTS 
MALTOSE 

PARTS 
LACTOSE 

124 

55-1 

90.3 

78.5 

178 

79-5 

130.3 

"3-3 

I25 

55-6 

91.1 

79.1 

179 

80.0 

131.0 

II3-9 

126 

56.0 

91.8 

79.8 

180 

80.4 

131.8 

114.6 

127 

56.5 

92.5 

80.4 

181 

80.8 

132.5 

115.2 

128 

56-9 

93-3 

81.1 

182 

81.3 

133-2 

115.8 

129 

57-3 

94.0 

81.7 

183 

81.8 

134.0 

116.5 

130 

57-8 

94-8 

82.4 

184 

82.2 

134-7 

117.1 

I3I 

58.2 

95-5 

83.0 

185 

82.7 

*35-5 

117.8 

132 

58.7 

96.2 

83.6 

186 

83.1 

136.2 

118.4 

133 

59-1 

97.0 

84.2 

187 

83.5 

136.9 

119.1 

J34 

59-6 

97-7 

84.9 

188 

84.0 

137.7 

119.7 

*35 

60.0 

98.4 

85.5 

189 

84.4 

138.4 

120.4 

136 

60.5 

99.2 

86.1 

190 

84.9 

I39.I 

I2I.O 

137 

60.9 

99.9 

86.8 

191 

854 

139.9 

I2I.7 

138 

61.3 

100.7 

87.4 

192 

85.9 

140.6 

122.3 

139 

61.8 

101.4 

88.1 

193 

86.3 

141.4 

123.0 

140 

62.2 

102.  1 

88.7 

194 

86.8 

142.1 

123.6 

141 

62.7 

102.8 

89.3 

195 

87.2 

142.8 

124.3 

142 

63.1 

103.5 

90.0 

196 

87.7 

143.6 

124.9 

143 

63.6 

104.3 

90.6 

197 

88.1 

144.3 

125.6 

144 

64.0 

105.0 

91-3 

198 

88.6 

I45-I 

126.2 

145 

64-5 

105.8 

91.9 

199 

89.0 

145.8 

126.9 

146 

64.9 

106.5 

92.6 

200 

89.5 

146.6 

127.5 

147 

65-4 

107.2 

93-2 

201 

89.9 

147-3 

128.2 

148 

65.8 

108.0 

93-9 

202 

90.4 

148.1 

128.8 

149 

66.3 

108.7 

94-5 

203 

90.8 

148.8 

129.5 

15° 

66.8 

109.5 

95-2 

204 

91-3 

149.6 

I30.I 

151 

67-3 

1  10.2 

95-8 

205 

91.7 

150-3 

130.8 

152 

67.7 

1  1  1.0 

96.5 

206 

92.2 

151.1 

I3L5 

153 

68.3 

111.7 

97.1 

207 

92.6 

151.8 

I32.I 

154 

68.7 

112.4 

97-8 

208 

93-1 

152.5 

132.8 

155 

69.2 

113.2 

984 

209 

93-5 

153.3 

!334 

J56 

69.6 

113.9 

99.1 

2IO 

94.0 

i54.i 

I34.I 

157 

70.0 

114.7 

99-7 

211 

944 

154.8 

134.7 

158 

70.5 

"54 

100.4 

212 

94.9 

155.6 

1354 

159 

70.9 

116.1 

10  1.  0 

213 

95-3 

156-3 

136.0 

160 

71-3 

116.9 

101.7 

2I4 

95-8 

I57-I 

136.7 

161 

71.8 

117.6 

102.3 

215 

96.3 

157.8 

137.3 

162 

72.3 

118.4 

103.0 

216 

96.7 

158.6 

138.0 

163 

72.7 

119.1 

103.6 

217 

97-2 

159.3 

138.6 

164 

73-2 

119.9 

104.3 

218 

97.6 

1  60.0 

139.3 

165 

73-6 

120.6 

104.9 

219 

98.1 

160.8 

139.9 

166 

74.1 

121.4 

105.6 

220 

98.6 

161.5 

140.6 

167 

74-5 

1  22.  1 

106.2 

221 

99.0 

162.3 

141.2 

1  68 

74-9 

122.9 

106.9 

222 

99-5 

163.0 

141.9 

169 

754 

123.6 

107.5 

223 

99.9 

163.7 

142.5 

170 

75-8 

1244 

108.2 

224 

100.4 

164.5 

143.2 

171 

76.3 

I25.I 

108.8 

225 

100.9 

165.3 

143.8 

172 

76.8 

125.8 

109.5 

226 

101.3 

166.0 

144-5 

173 

77.3 

126.6 

1  10.  1 

227 

101.8 

166.8 

I45-I 

174 

77-7 

127.3 

1  10.8 

228 

102.2 

167.5 

145.8 

175 

78.2 

I28.I 

111.4 

229 

102.7 

168.3 

146.4 

176 

78.6 

128.8 

1  12.0 

230 

I03.I 

169.1 

147.0 

177 

79.1 

129.5 

1  1  2.6 

23T 

103.6 

169.8 

147.7 

306 


TABLES 


PARTS  COPPER 
OXIDE 

PARTS 
DEXTROSE 

PARTS 

MALTOSE 

PARTS 
LACTOSE 

PARTS  COPPER 
OXIDE 

PARTS 
DEXTROSE 

PARTS 
MALTOSE 

PARTS 
LACTOSE 

232 

104.0 

170.6 

148.3 

277 

124.6 

204.5 

177.6 

233 

104.5 

I7L3 

149.0 

278 

125.1 

205.2 

178.3 

234 

105.0 

172.1 

149.6 

279 

125.6 

206.0 

178.9 

235 

105.4 

172.8 

150.3 

280 

126.1 

206.8 

179.6 

236 

105-9 

173.6 

150.9 

281 

126.5 

207.5 

180.2 

237 

106.3 

174-3 

151.6 

282 

127.0 

208.3 

180.9 

238 

106.8 

I75.I 

152.2 

283 

127.4 

209.0 

181.5 

239 

107.2 

175-8 

152.9 

284 

127.9 

209.8 

182.2 

240 

107.7 

176.6 

153-5 

285 

128.3 

210.5 

182.9 

241 

I08.I 

177-3 

154.2 

286 

128.8 

211.3 

183.6 

242 

108.6 

178.1 

154.8 

287 

129.3 

2I2.I 

184.2 

243 

109.0 

178.8 

155.5 

288 

129.7 

212.8 

184.9 

244 

109.5 

179.6 

156.1 

289 

130.2 

213.6 

185.6 

245 

109.9 

180.3 

156.8 

290 

130.6 

214-3 

186.2 

246 

110.4 

181.1 

157-4 

291 

131.1 

2I5.I 

186.9 

247 

110.9 

181.8 

158.1 

292 

I3L5 

*  215.9 

187.6 

248 

IH.3 

182.6 

158.7 

293 

132.0 

216.6 

188.2 

249 

iii.S 

183-3 

159-4 

294 

J32-5 

217.4 

188.9 

250 

112.3 

184.1 

160.0 

295 

!33.o 

218.2 

189.5 

251 

112.7 

184.8 

160.7 

296 

133-4 

218.9 

190.2 

252 

113.2 

185.5 

161.3 

297 

133.9 

219.7 

190.8 

253 

II3-7 

186.3 

162.0 

298 

!34«3 

220.4 

J9i-5 

254 

114.1 

187.1 

162.6 

299 

134.8 

221.2 

192.1 

255 

114.6 

187.8 

163-3 

300 

135-3 

221.9 

192.8 

256 

115.0 

188.6 

163.9 

301 

135-7 

222.7 

193-4 

257 

II5-5 

189.3 

164.6 

302 

136.2 

223.5 

194.1 

258 

116.0 

190.1 

165.2 

303 

136.6 

224.2 

194.7 

259 

116.4 

190.8 

165.9 

3°4 

I37.I 

225.0 

J95-3 

260 

116.9 

191.6 

166.5 

305 

137.6 

225.8 

196.0 

261 

II7-3 

192.4 

167.2 

306 

138.0 

226.5 

196.6 

262 

117.8 

I93.I 

167.8 

3°7 

138.5 

227.3 

197-3 

263 

118.3 

193-9 

168.1 

308 

138.9 

228.1 

197.9 

264 

118.7 

194.6 

169.5 

309 

139.4 

228.8 

198.6 

265 

119.2 

1954 

169.8 

310 

139.9 

229.6 

199.3 

266 

119.6 

196.1 

170.4 

3H 

140.3 

230.4 

199.9 

267 

1  20.  1 

196.9 

171.1 

312 

140.8 

23I.I 

200.6 

268 

120.6 

197.7 

171.7 

313 

141.2 

231.9 

201.3 

269 

I2I.O 

198.4 

172.4 

314 

141.7 

232.7 

202.0 

270 

I2I.4 

199.2 

173.0 

315 

142.2 

233-4 

202.6 

271 

I2I.9 

199.9 

173-7 

316 

142.6 

234.2 

203.3 

272 

122.4 

200.7 

174.4 

317 

143.  i 

234-9 

203.9 

273 

122.8 

201.5 

175.0 

318 

143.6 

235-7 

204.6 

274 

123.3 

2O2.2 

175-7 

319 

144.0 

236.5 

205.3 

275 

123.7 

203.0 

176.3 

320 

144.5 

237.2 

205.9 

276 

124.2 

203.7 

177.0 

TABLES 


307 


5. —  CALCULATED  VALUES  OF  CUPRIC-REDUCING  POWERS  AND 
PARTS  OF  MALTOSE,  DEXTROSE,  AND  DEXTRIN  PER  UNIT 
OF  CARBOHYDRATE  FOR  EACH  DEGREE  OF  ROTATION 
OF  A  NORMALLY  ACID  HYDROLYZED  STARCH  SOLUTION 


rap° 

1    JD  386 

*386* 

m 

386 

V 

A 

386 

195 

0.000 

0.000 

0.000 

1.  000 

194 

O.OII 

0.017 

O.OOI 

0.982 

193 

0.022 

0.038 

0.00  1 

0.966 

192 

0.032 

0.052 

O.OOI 

0.947 

I9I 

0.041 

0.068 

0.002 

0.930 

I9O 

0.051 

0.084 

0.002 

0.914 

189 

0.061 

0.098 

O.OO2 

0.900 

188 

0.071 

0.114 

0.003 

0.883 

187 

0.081 

0.128 

OiOOS 

0.869 

186 

0.090 

0.143 

0.005 

0.852 

185 

O.IOO 

0.157 

0.005 

0.838 

184 

0.109 

0.170 

0.008 

0.822 

183 

0.118 

0.183 

0.010 

0.807 

182 

0.127 

0.195 

O.OI2 

0.793 

181 

0.137 

0.207 

0.014 

0.779 

180 

0.146 

0.219 

0.016 

0.765 

179 

0.155 

0.227 

0.019 

0.754 

178 

0.164 

0.237 

0.022 

0.741 

177 

0.173 

0.247 

O.O24 

0.729 

176 

0.182 

0.257 

0.027 

0.716 

175 

0.191 

0.266 

O.O3I 

0.705 

174 

0.199 

0.274 

0.034 

0.692 

173 

0.207 

0.282 

0.038 

0.680 

172 

0.216 

0.290 

0.042 

0.668 

171 

0.224 

0.298 

0.046 

0.656 

170 

0.233 

0.305 

0.050 

0.645 

169 

0.242 

0.312 

0.053 

0.635 

168 

0.251 

0.318 

0.056 

0.625 

167 

0.259 

0.325 

0.060 

0.615 

166 

0.267 

0.331 

0.064 

0.605 

165 

0.275 

0.337 

0.068 

o-595 

164 

0.283 

0.343 

0.073 

0.584 

163 

0.292 

0.350 

0.076 

0.572 

162 

0.300 

0.356 

0.083 

0.561 

161 

0.308 

0.362 

0.088 

o-55o 

160 

0.316 

0.367 

0.093 

0.540 

159 

0.324 

0.374 

0.098 

0.528 

158 

0.332 

0.381 

O.IO2 

0-517 

157 

0.340 

0.387 

0.106 

0.507 

156 

0.348 

0.392 

O.IIO 

0.498 

155 

0-356 

0.397 

0.115 

0.488 

154 

0-365 

0.402 

O.I2O 

0.478 

153 

0-373 

0.407 

0.125 

0.468 

*  Obtained  by  Defren's  Reduction  Method. 


308 


TABLES 


fal20 

1    JD  386 

*386 

m 

386 

.% 

A386 

152 

0.381 

0.412 

0.130 

0.458 

151 

0.389 

0.414 

o.i35 

0.451 

150 

0-397 

0.421 

0.140 

0-439 

149 

0.404 

0.425 

0.146 

0.429 

148 

0.412 

0.429 

0.152 

0.419 

147 

0.419 

0.432 

0.158 

0.410 

146 

0.427 

o-434 

0.163 

0.403 

145 

0-435 

0.436 

0.169 

0-395 

144 

0.442 

0-439 

0.175 

0.386 

143 

0.450 

0.442 

0.183 

0-375 

142 

0.458 

0.445 

0.188 

0.367 

I4I 

0.465 

0.448 

0.193 

0-359 

140 

0-473 

0.450 

0.199 

0.351 

139 

0.481 

0.452 

0.206 

0.342 

138 

0.488 

0.454 

0.212 

0.334 

137 

0.496 

0.456 

O.2I9 

0.325 

136 

0.503 

0.458 

0.224 

0.318 

J35 

0.510 

0.459 

O.23O 

0.3II 

134 

OW 

0-459 

0.237 

0.304 

i33 

0.524 

0.460 

0.244 

0.296 

132 

0-531 

0.460 

0.250 

0.290 

131 

0.538 

0.461 

0.257 

0.282 

130 

0.546 

0.462 

0.264 

0.274 

129 
128 

0-553 
0.560 

0.462 
0.462 

O.272 
0.279 

0.266 
0.258 

127 

0.567 

0.461 

0.287 

0-253 

126 

0-574 

0.460 

0.294 

0.246 

125 

0.580 

0.460 

0.301 

0.239 

124 

0.588 

0.459 

0.308 

0.233 

123 

0-595 

0.458 

0.315 

0.227 

122 

0.602 

0.456 

0.323 

0.221 

121 

0.608 

0-455 

0.331 

O.2I4 

I2O 

0.614 

0-453 

0.338 

0.209 

119 

0.621 

o.45i 

0.346 

0.203 

118 

0.628 

0.450 

0-354 

0.196 

II7 

0-635 

0.448 

0.361 

O.I9I 

116 

0.642 

0.446 

0.369 

0.185 

"5 

0.649 

0.444 

0.377 

0.178 

114 

0.656 

0.442 

0.387 

O.I7I 

113 

0.663 

0.439 

0-395 

0.166 

112 

0.669 

0.436 

0.403 

0.161 

III 

0.675 

o-433 

0.4II 

0.156 

1  10 

0.681 

0.429 

0.420 

0.152 

109 

0.687 

0.425 

0.428 

0147 

108 

0.694 

0.421 

0.436 

0.143 

107 

0.700 

0.418 

0-445 

0.137 

106 

0.707 

0.414 

0-453 

0.133 

105 

0.713 

0.411 

0.462 

0.127 

104 

0.719 

0.407 

0.471 

O.I22 

103 

0.725 

0.402 

0.480 

O.II8 

102 

0.732 

0.398 

0.489 

O.II3 

101 

0.738 

0-393 

0.498 

0.109 

100 

0.744 

0.389 

0.508 

0.103 

99 

0.75° 

0.384 

0.518 

0.099 

TABLES 


309 


[a]20 
JD386 

V 

m 

386 

** 

A 

386 

98 

0-757 

0.380 

0.527 

0.093 

97 

0.763 

0-374 

0.536 

0.090 

96 

0.769 

0.368 

0.545 

0.087 

95 

0-775 

0.362 

0.554 

0.084 

94 

0.781 

0-357 

0.563 

0.080 

93 

0.787 

0-352 

0.572 

0.076 

92 

0-793 

0-347 

0.581 

0.072 

9i 

0.799 

0.342 

0.591 

0.068 

90 

0.805 

0.336 

0.600 

0.064 

89 

0.810 

0.329 

0.610 

0.061 

88 

0.816 

0.322 

0.620 

0.058 

87 

0.822 

0.315 

0.630 

o-055 

86 

0.828 

0.308 

0.640 

0.052 

85 

0.834 

0.302 

0.650 

0.048 

84 

0.839 

0.294 

0.660 

0.044 

83 

0.844 

0.287 

0.670 

0.043 

82 

0.850 

0.279 

0.680 

0.041 

81 

0.856 

0.272 

0.690 

0.038 

80 

0.862 

0.264 

0.701 

0.035 

79 

0.867 

0.256 

0.712 

0.032 

78 

0.872 

0.247 

0.722 

0.031 

77 

0.878 

0.237 

0-733 

0.030 

76 

0.884 

0.228 

0.744 

0.028 

75 

0.889 

0.219 

0-755 

0.026 

74 

0.895 

0.210 

0.766 

0.024 

73 

0.901 

0.199 

0.778 

0.023 

72 

0.906 

0.189 

0.789 

0.022 

71 

0.911 

0.179 

0.801 

0.02O 

70 

0.916 

0.170 

0.811 

O.OI8 

69 

0.921 

0.159 

0.824 

0.017 

68 

0.926 

0.149 

0.835 

0.016 

67 

0.932 

0.139 

0.846 

0.015 

66 
65 

0-937 
0.942 

0.130 
O.I2I 

0.856 
0.867 

0.014 
O.OI2 

64 

0.947 

O.IIO 

0.879 

O.OII 

63 

0.952 

0.099 

0.890 

O.OII 

62 

0-957 

0.088 

0.902 

O.OIO 

61 

0.962 

0.078 

0.914 

0.008 

60 

0.967 

0.068 

0.926 

0.006 

59 

0.972 

0.°57 

0-937 

O.OO6 

58 

0.977 

0.047 

0.948 

0.005 

57 

0.982 

0.036 

0.960 

O.OO4 

56 

0.987 

0.025 

0.971 

0.004 

55 

0.992 

O.OI5 

0.982 

0.003 

54 

0.997 

0.005 

0-993 

0.002 

53 

1.  000 

o.ooo 

I.OOO 

O.OOO 

3io 


TABLES 


6.  — DENSITY   OF   WATER  AT   DIFFERENT  TEMPERATURES 


TEMPERATURE: 
DEGREES  CENTIGRADE 

DENSITY  OF  WATER 
RELATIVE  TO  ITS  DEN- 
SITY AT  4°  C. 

TEMPERATURE: 
DEGREES  CENTIGRADE 

DENSITY  OF  WATER 
RELATIVE  TO  ITS  DEN- 
SITY AT  4°  C. 

0° 

0.99987 

27° 

0.99660 

I 

0.99993 

28 

0.99633 

2 

0.99997 

29 

0.99605 

3 

0.99999 

30 

0-99577 

4 

1.  00000 

31 

0.99547 

5 

0.99999 

32 

0.99517 

6 

0.99997 

33 

0.99485 

7 

0.99993 

34 

0.99452 

8 

0.99989 

35 

0.99418 

9 

0.99982 

36 

0.99383 

10 

0.99975 

37 

0-99347 

ii 

0.99966 

38 

0.99310 

12 

0.99955 

39 

0.99273 

13 

0.99943 

40 

0.99235 

14 

0.99930 

41 

0.99197 

15 

0.99916 

42 

0.99158 

15.5 

0.99908 

43 

0.99II8 

16 

0.99900 

44 

0.99078 

17 

0.99884 

45 

0.99037 

17.5 

0.99875 

46 

0.98996 

18 

0.99865 

47 

0.98954 

19 

0.99846 

48 

o  98910 

20 

0.99826 

49 

0.98865 

21 

0.99805 

5° 

0.98819 

22 

0.99783 

00 

0.98334 

23 

0.99760 

70 

0.97790 

24 

0.99737 

80 

0.97191 

25 

0.99712 

90 

0.96550 

26 

0.99687 

100 

0.95863 

The  temperature  readings  are  those  given  by  a  mercury  thermometer. 
Landolt's  table  refers  to  hydrogen  thermometer  readings.  The  readings  of 
the  two  thermometers  agree  at  o  and  100°.  At  20°  the  mercury  thermometer 
reads  about  0.1°  less  than  the  hydrogen. 


TABLES 


7.— VOLUMES     OF     SUGAR     SOLUTIONS     AT     TEMPERATURES 

BETWEEN  o°   AND    100°   C    (Mercury  thermometer} 

(Volume  at  o°  =  i.     Gerlach.) 


TEMP. 
°C. 

0% 

5% 

10% 

15% 

20% 

25% 

30% 

35% 

0 

1.  00000 

1.  00000 

1.  00000 

i  .00000 

I.OOOOO 

I.OOOOO 

I.OOOOO 

I.OOOOO 

5 

0.99989 

1.00013 

1.00028 

1.00043 

1.00053 

1.00063 

1.00083 

1.00093 

10 

1.00013 

1.00046 

1.00076 

1.00106 

1.00136 

1.00161 

1.00186 

1.00216 

15 

1.00070 

1.00114 

1.00159 

1.00199 

1.00239 

1.00289 

1.00319 

1.00359 

17-5 

I.OOIIO 

1.00170 

I.002IO 

1.00260 

1.00305 

L00355 

1.00405 

1.00445 

20 

1.00160 

1.00232 

I.0027I 

1.00332 

1.00382 

1.00432 

1.00482 

1.00522 

25 

1.00275 

1.00365 

I.OO4I5 

1.00475 

1.00535 

1.00595 

1.00650 

1.00695 

30 

1.00415 

1.00508 

1.00568 

1.00638 

1.00698 

1.00768 

1.00823 

1.00878 

35 

1-00575 

1.  0068  1 

I.0074I 

i.  008  1  1 

1.00881 

1.00951 

I.OIOII 

1.01071 

40 

1.00755 

1.00864 

1.00934 

1.01014 

1.01084 

.OH55 

I.OI22O 

1.01280 

45 

1.00955 

1.01077 

I.OH53 

1.01228 

1.01308 

.01378 

I.OI443 

1.01503 

5o 

1.01175 

1.01301 

I.OI38I 

1.01461 

1.01541 

.01616 

1.01676 

1.01737 

55 

1.01415 

1.01544 

I.OI624 

1.01704 

1.01785 

.01865 

I.OI925 

1.01980 

60 

1.01675 

1.01808 

I.OI878 

1.01958 

1.02038 

.02118 

1.02160 

1.02233 

65 

1.01955 

1.02081 

I.02I4I 

1.02232 

1.02302 

.02382 

1.02447 

1.02497 

70 

1,02255 

1.02365 

1.02425 

1.02515 

1.02575 

.02655 

1.02721 

1.02771 

75 

1.02570 

i  .02669 

I.027I9 

1.02809 

1.02869 

.02939 

1.03004 

1.03054 

80 

1.02900 

1.02973 

1.03033 

1.03113 

1.03183 

1.03243 

1.03303 

1.03348 

85 

1.03240 

1.03307 

1.03367 

1-03437 

1-03517 

1.03567 

1.03017 

1.03657 

90 

1.03585 

1.03661 

I.0372I 

1.03781 

1.03861 

1.03911 

1-03951 

1.03976 

95 

1.03930 

1.04035 

1.04085 

1.04145 

1.04215 

1.04255 

1.04286 

1.04311 

IOO 

1.04275 

1.04409 

1.04459 

1.04520 

1.04570 

1.04600 

1.04630 

1.04660 

TEMP 

°C. 

40% 

45% 

50% 

55% 

60% 

65% 

70% 

75% 

0 

1.  00000 

1.  00000 

I.OOOOO 

I.OOOOO 

I.OOOOO 

I.OOOOO 

I.OOOOO 

I.OOOOO 

5 

1.00113 

1.00133 

1.00153 

1.00163 

1.00173 

1.00173 

1.00178 

1.00183 

10 

1.00246 

1.00276 

1.00306 

1.00326 

1.00341 

1.00351 

1.00356 

1.00366 

15 

1.00399 

1.00434 

1.00469 

1.00494 

1.00514 

1.00529 

1.00539 

1.00549 

17.5 

1.00480 

1.00515 

1.00550 

1.00581 

1.00606 

1.  00616 

1.00626 

1.00641 

20 

1.00562 

1.00602 

1.00642 

1.00667 

1.00692 

1.00712 

1.00722 

1.00732 

25 

1.00735 

1.00785 

1.00825 

1.00850 

1.00800 

1.00895 

1.00905 

1.00920 

30 

1.00918 

1.00978 

1.01018 

1.01043 

1.01073 

1.01098 

1.01093 

1.01113 

35 

1.01116 

1.01182 

I.OI222 

1.01247 

1.01277 

1.01302 

I  01287 

1.01312 

40 

1.01335 

1.01395 

I-OI435 

1.01460 

1.01490 

1.01515 

1.01485 

1.01515 

45 

1.01558 

1.01623 

I.OI658 

1.01683 

1.01713 

1.01728 

1.01688 

1.01728 

50 

1.01791 

1.01862 

I.OI892 

1.01917 

1.01947 

1.01952 

1.01912 

1.01952 

55 

1.02045 

1.02115 

I.02I35 

1.02160 

1.02190 

1.02185 

1.02135 

1.02175 

60 

1.02309 

1.02369 

1.02389 

1.02414 

1.02434 

1.02419 

1.02379 

1.02409 

65 

1.02572 

1.02632 

1.02642 

1.02667 

1.02687 

1.02662 

1.02622 

1.02642 

70 

1.02846 

1.02906 

1  .02906 

1.02931 

1.02941 

1.02916 

1.02886 

1.02886 

1S 

1.03120 

1.03190 

I.03I80 

1.03195 

1.03205 

1.03170 

1.03150 

1.03130 

80 

1.03403 

1.03484 

1.03464 

1.03469 

1.03479 

L03434 

1.03419 

1.03383 

85 

1.03697 

1.03788 

L03758 

1  -03743 

1.03763 

1.03707 

1.03687 

1.03647 

90 

1.04007 

1.04092 

1.04062 

1.04032 

1.04052 

1.03991 

1.03961 

1.03911 

95 

I-°433I 

1.04406 

1.04376 

1.04336 

1.04346 

1.04276 

1.04256 

1.04185 

IOO 

1.04670 

1.04720 

I.O47OO 

1.04640 

1.04650 

1.04570 

1.04550 

1.04459 

312 


TABLES 


-TABLES   FOR  CALCULATING   THE   PER   CENT   OF   INVERT 
SUGAR   IN    PRESENCE   OF    SUCROSE   FROM   THE   COPPE 
PRECIPITATED  IN  HERZFELD'S  REDUCTION  METHOD   BY 
10  GRAMS  OF  SAMPLE 

A.  —When  less  than  one  per  cent  of  invert  sugar  is  in  sample. 


— 

MG.  COPPER 

PER  CENT 
INVERT  SUGAR 

MG.  COPPER 

PER  CENT 
INVERT  SUGAR 

.05 

155 

•59 

65 

.07 
.09 
.11 

160 
165 
170 

£ 

70 

75 
go 

•14 
.16 

175 
180 

185 

i 

85 
9° 

.21 
.24 

190 
195 

•79 
.82 

95 

100 

.27 

•3° 

02 

200 
205 
2IO 

[90 

no 
"5 

120 
125 
130 
135 
140 

•35 
.38 
.40 

•43 
45 
48 

215 
220 
225 
230 

235 
240 

245 

•93 
.96 
•99 

1.02 
1.05 
1.07 
1.  10 

145 

•53 

15° 

.56 

TABLES 


313 


B.  —  Invert  sugar  factors  when  more  than  one  per  cent  of  invert  sugar  is 

in  sample. 


RATIO  OF  SUCROSE 
TO  INVERT  SUGAR 

APPROXIMATE  WEIGHT  OF  INVERT  SUGAR  CORRESPONDING  TO  THE 

COPPER   ACTUALLY   WEIGHED    lz——) 

R   :    Y 

200  mg. 

175  mg- 

150  mg. 

125  mg. 

100  mg. 

75  mg. 

50  mg. 

0          ICO 

56.4 

55-4 

54-5 

53-8 

53-2 

53-0 

53-o 

10        90 

56.3 

55-3 

54-4 

53-8 

53-2 

52-9 

52-9 

20             80 

56.2 

55-2 

54-3 

53-7 

53-2 

52-7 

52.7 

30             70 

56.1 

55-i 

54-2 

53-7 

53-2 

52.6 

52.6 

40             60 

55-9 

55-0 

54-i 

53-6 

53-i 

52.5 

52.4 

5°         5° 

55-7 

54-9 

54-° 

53-5 

53-i 

52.3 

52.2 

60         40 

55-6 

54-7 

533 

53-2 

528 

52.1 

519 

70         30 

55-5 

54-5 

53-5 

52-9 

52-5 

5i-9 

51.6 

80             20 

55-4 

54-3 

53-3 

52.7 

52.2 

5i-7 

5i-3 

90         10 

54-6 

53-6 

53-i 

52-6 

52  i 

5i-6 

51.2 

91           9 

54-i 

53-6 

52.6 

52.1 

51.6 

51-2 

50.7 

92           8 

53-6 

53-i 

52.1 

51.6 

51-2 

50-7 

50.3 

93           7 

53-6 

53-i 

52-1 

51.2 

5i-7 

50-3 

49-8 

94           6 

53-i 

52.6 

51.6 

5o-7 

503 

49-8 

48.9 

95          5 

52  6 

52.1 

51.2 

50-3 

49-4 

48.9 

48.5 

96           4 

52.1 

51.2 

50-7 

49-3 

48.9 

47-7 

46.9 

97           3 

5o-7 

5o-3 

49-8 

48.9 

47  7 

46.2 

45-1 

98           2 

49-9 

48.9 

48.5 

47-3 

45  8 

43-3 

40.0 

99           i 

47-7 

47-3 

46.5 

45-i 

43-3 

41.1 

38.1 

Explanation  of  Table  B.  —  The  cupric-reducing  power  of  an  invert  sugar 
solution  is  not  only  dependent  on  the  concentration  of  the  invert  sugar  itself, 
but  is  also  affected  by  the  amount  of  sucrose  present.  Hence,  in  order  to  deter- 
mine the  factor  for  calculating  the  exact  weight  of  invert  sugar  corresponding  to 
the  copper  precipitated,  it  is  necessary  to  have  a  convenient  way  of  making  a 
rough  preliminary  estimation  of  the  invert  sugar  weight,  so  that  the  approxi- 
mate ratio  of  the  invert  sugar  to  sucrose  may  be  known. 

The  approximate  weight  of  invert  sugar  (Z)  is  one  half  of  the  precipitated 
copper  (Cu).  The  weight  of  invert  sugar  so  found,  divided  by  the  weight  of 
sample  (  W}  in  50  cc.  of  the  solution  taken  for  Fehlingtest,  is  the  approximate 
per  cent  of  invert  sugar  (i)  in  the  sample.  The  polarization  of  the  sample 
(P)  is  taken  as  the  per  cent  of  sucrose.  The  ratio  of  the  per  cents  of  sucrose 
and  invert  sugar  so  found  is  expressed  in  parts  per  hundred  of  the  sum  of 
these  percentages,  and  the  nearest  corresponding  ratio  (A':  Y)  is  found  in  the 
left-hand  column  of  Table  B.  The  factor  (F)  in  this  table  corresponding  to 
this  ratio,  in  the  column  under  the  weight  approximating  most  nearly  to  the 
weight  of  invert  sugar  (Z),  is  multiplied  by  the  weight  of  copper  (Cu)  to  give 
the  exact  per  cent  of  invert  sugar  (/)  in  the  sample. 

Expressed  algebraically : 

y  CU  100    Z 


t= 


FCu 

W 


314  TABLES 


OPTICAL  ROTATION   CONSTANTS   FREQUENTLY  USED 

Sucrose,     [o]^  =  66.67°  ""  -°°9S  w  (™>  4-5  to  22.7). 

(When  w  is  taken  as  the  weight  of  sugar  in  grams  in  100  Mohr  cc.,  the 
equation  becomes  [a]17-5  =  66.82°  —  .0096  w.     This  of  course  is  not  the 

true  specific  rotation,  but  is  a  convenient  constant  for  saccharimetnc 
calculations.) 

Temperature  formula :    [a^]  =  [a]^°  —  .0114  (/  —  20). 

Lactose,     [a]20  =  52.53°.     (Veiy  slight  change  with  variation  in  concentra- 
tion.)    Temperature  formula:    [a]*  =  [a]20  —  .070(20  —  f). 
Maltose,     [a]     =  140.375°  —  .oi837/  —  .095  /. 
Raffinose.     [a]2^  =  104.5°. 
Dextrose,     [a]17  =  52.50°  +  .01 8796^  +•  .00051683/20       (Little   affected   by 

temperature  change.) 
Invert  sugar,     [a]^0  =  —  19.82  —  .04 /.     [a]^  =  —  27.9  -f-  .32*. 

Quartz,     [a]*  =  21.72°  (i  +  .000143  (20  —  /)). 


INDEX 


Absolute  specific  rotation,  245. 
Accuracy  of  saccharimetry,  39. 
Acid  hydrolysis,  lactose,  102;  laws,  198, 

252;     maltose,    102;     raffinose,    108 ; 

speed,  252;  starch,  174;  sucrose,  103  j 

temperature  influence,  254. 
Acidity,  juice,  122. 

Afifinity  constants,  251 ;  by  starch  hydrol- 
ysis, 255  ;  by  sucrose  hydrolysis,  252. 
Alkaloids,  262 ;  brucine,  248  ;  chinchoni- 

dine,  264 ;  cocaine,  265  ;  nicotine,  266 ; 

quinine,  264 ;  strychnine,  248  ;  used  in 

synthesis,  243. 

Alumina,  mixture  for  clarifying,  90. 
Analyzer,  8. 

Andrews's  temperature  corrections,  43. 
Angular  degree  scales,  n,  29. 
Antipodes,  239 ;  separation  of,  243. 
Apparent  quotient  of  purity,  153. 
Arabinose,  251. 
Ash,  determination  in  beet  juices,  150; 

glucose,  193;  density  correction,  194. 
Asparagine  in  cane  juice,  125. 
Assymmetric  carbon,  240. 

Bagasse,  114;  fibre  in,  124. 

Bag  filters,  156. 

Balance,  39,  53 ;  specific  gravity,  186. 

Barrel  sirup,  157. 

Basic  lead  acetate  solution,  54. 

Beaume  hydrometers,  128;  for  glucose 
industry,  208 ;  table,  285. 

Beet  juice,  146;  diffusion,  145. 

Beet  molasses,  148  ;  sugar  from,  148. 

Beet  sugar,  147;  export,  in,  155;  valua- 
tion, 155. 

Beets,   144;    sugar  determination,   149; 


sampling,  149. 
Bibliography,  reference  books,  279; 

papers  on  saccharimetry,  100;  papers 

on  starch,  221. 
Biose  sugars,  101. 


Biot,  17 ;  light  wave  value,  19 ;  solution 
formulae,  245. 

Boiling  blank,  135. 

Bone  black,  157 ;  in  saccharimetry,  91 ; 
filters,  156-  spent  ("spent  black"), 
158,  207. 

Borneol,  269. 

British  gum,  219. 

Brix  hydrometers  (spindles),  117;  con- 
venient size,  55;  reading,  118;  tem- 
perature corrections,  55,  295;  tables, 
285  ;  in  glucose  analysis,  194. 

Brown's  researches  in  starch,  174,  192, 
199,  221. 

Brucine  salts,  248. 

Cadinene,  268. 

Calc  spar  (see  Iceland  spar). 

Calculation  of  errors,  39,  63. 

Calibration  of  flasks,  Mohr  cc.,  56;  true 
cc.,  57. 

Calibration  of  saccharimeters,  41,  45. 

Camphene,  267. 

Camphor,  247,  270 ;  in  celluloid,  261. 

Cane  culture,  112;  fibre,  114;  fibre  deter- 
mination, 124;  mills,  114;  sampling, 
113;  seedling,  112;  sour,  123;  valua- 
tion, 113. 

Cane  juice,  114;  classification,  125;  com- 
position, 115  ;  extraction,  115,  123,  139 ; 
unripe,  122,  140. 

Carbonatation,  146. 

Carvone,  270. 

Caryophyllene,  268. 

Celluloid,  camphor  in,  261. 

Cellulose  hydrolysis,  235. 

Centrifugal  machines,  132,  133,  147,  156, 


208. 

Centrifugal  sugars,  88,  155. 
Chandler   and    Ricketts's    detection 

glucose,  226. 
Citral,  272. 

315 


of 


INDEX 


Citronellal,  270. 

Citronellol,  268. 

Clarification,  beet  juice,  146 ;  cane  juice, 
125;  Deming  process,  126;  errors,  96; 
glucose,  206 ;  in  saccharimetry,  89,  90 ; 
Horn's,  90. 

Clarifier  (see  defecator). 

Clerget  method,  principles,  104 ;  original, 
105 ;  Herzfeid's,  107 ;  Tolman's  inves- 
tigation, 108  ;  applied  by  Leach,  232. 

Cocaine,  265. 

Concentration,  formulas,  12,  13 ;  errors 
in  saccharimetry,  98  ;  influence  on  rota- 
tion, 5,  IT,  244 ;  juices,  128  ;  glucose,  208. 

Confectionery  analysis,  228. 

Constants  of  rotation,  12. 

Control-tube,  41 ;   manipulation,  94. 

Corn  for  starch  manufacture,  212. 

Creatinin  in  urine,  236. 

Creydt's  rafrinose  method,  109;  modifi- 
cations, 109. 

Crystallization,  in  vacuum  pans,  130; 
effect  on  rotation,  i ;  in  wagons,  135. 

Crystallizers,  135. 

Crusher,  cane,  114. 

Cubic  centimeter,  Mohr,  30,  40,  56,  58 ; 
true,  30,  40,  46,  57,  58. 

Cupric-reducing  power,  172;  determi- 
nation, 196;  relation  to  rotation,  183; 
table  for  acid-hydrolized  starch,  307. 

Cupric-reduction  table,  Defren's,  304. 

Defecation  (see  clarification). 

Defecator,  125 ;  tallies,  142. 

Defren,  169,  171,  200;  Periling  method, 
169 ;  reduction  table,  304. 

Deming  process,  127. 

Density,  186;  by  Brix  spindle,  118,  120; 
by  pyknometer,  189;  table  for  sugar 
solutions,  285 ;  by  Westphal  balance, 
186;  of  water,  310;  factors  for  starch 
products,  185 ;  factors,  assumed,  185, 
191. 

Dextrose,  102,  109, 174, 175,  176, 179, 180; 
commercial,  208 ;  from  rafnnose,  109 ; 
from  sucrose,  102;  from  starch,  174; 
multirotation,  249,  251;  specific  rota- 
tion, 237,  314;  standard  solution,  163; 
table  for  Fehling  determination,  304; 
table  for  determination  in  hydrolyzed 
starch,  307. 


Diamyl,  i. 

Diastase  hydrolysis,  174, 183 ;  speed,  257, 

Diffusion,  145. 

Doolittle  torsion  viscosimeter,  215. 

Double  dilution,  97. 

Double  polarization  (see  Clerget). 

Double  refraction,  2;  calc  spar,  2; 
quartz,  22;  glass,  2,  42. 

Double-wedge  saccharimeter,  37;  ma- 
nipulation, 86. 

Drying  of  saccharine  products,  152. 

Eccentricity  errors,  40. 

End-point  device,  16;  Jellet-Cornu 
(Duboscq),  19;  Laurent,  22;  Lip- 
pich,  25 ;  Mitscherlich,  15 ;  transition 
tint,  16;  triple-shade,  78;  Wild,  26,  73. 

End-point  observations,  59. 

Entrainment,  133. 

Enzym  action,  102,  174. 

Errors,  63;  clarification,  55;  concentra- 
tion, 99;  cover  glass,  42 ;  eccentricity, 
40;  observation,  42;  of  saccharimetry, 
38,  96;  temperature,  43;  tube-length, 
39 ;  volume,  39 ;  weighing,  39 ;  zero, 
42,  44. 

Essential  (ethereal)  oils,  267  ;  terpene- 
less,  272. 

Extraction,  juice,  115,  139. 

Extraordinary  ray,  3. 

Fehling  method,  160;  gravimetric,  166; 
Defren's,  169 ;  Herzfeid's,  167 ;  Pavy's, 
165;  volumetric,  161. 

Fehling  solution,  161 ;  Soxhlet's,  161. 

Fenchone,  270. 

Fermentation  in  sugarhouse,  140. 

Fibre  in  cane,  114. 

Filar  micrometer,  71. 

Filter  cake,  weight,  128,  138 ;  sugar  in, 
127. 

Filter  press,  127. 

Filtering  solutions,  58. 

Filter,  ray,  Lippich,  n,  72,  259;  bi- 
chromate, 73,  77,  99;  brown  glass,  78, 

99, 

Fischer's  sugar  synthesis,  2,  240,  244. 
Flasks,  46,  54;   calibration,  56. 
Fluidity  of  starches,  215. 
Fondants,  229. 
Fric's  saccharimeter,  37. 


INDEX 


317 


Galactose,  102,  251. 

Gallotannic  acid,  273. 

Gauges,  recording,  143. 

Gauging  tanks,  141. 

Gill's  oleine  test,  273. 

Glucose,  commercial,  200;  clarification, 
206;  colorations,  209;  composition, 
201;  concentration,  208;  determina- 
tion, 192,  197,  226 ;  dispersive  effects, 

77,  106;  dyed,  209;  in  candy,  229;  in 
preserves,  232 ;  Japanese,  211 ;  loss  in 
manufacture,  212;    trade  forms,  201; 
polarization  correction,  107. 

Gommelin,  220. 

Graduations,  polariscope,  n,  60,  71 ; 
saccharimeter,  28,  29,  35,  46,  47,  60, 

78,  100,  259. 
Granulator,  147. 

Grape  sugar,  200;  trade  forms,  208. 
Gumdrops,  229. 

Half-shadow  device,  19;  sensitiveness, 
21  (see  also  end  point) . 

Heron  (see  Brown). 

Herschel's  law,  i. 

Herzfeld's  double  polarization,  107;  in- 
vert sugar  method,  167;  normal 
weight,  46. 

Honey,  225. 

Home's  clarification,  90. 

Hortvet's  maple  sugar  test,  228. 

Hot  room,  135. 

Hydrolysis,  102;  lactose,  102;  maltose, 
102,  255;  speed,  251;  starch,  174,  255, 
257 ;  sucrose,  102,  103 ;  temperature 
effect,  254. 

Hydrometers,  Beaume,  128;  Brix,  117; 
method  of  reading,  118. 

Iceland  spar  (calc  spar),  2,  26,  49. 

Intensity  of  light  in  Nicol,  8;  effect  of 
sugar  solution,  9. 

International  Sugar  Commission,  45, 
46. 

Inversion,  103  (see  also  hydrolysis). 

Invert  sugar,  103;  determination  by 
polarization,  108;  reduction  method, 
167;  in  cane  juices,  103;  specific 
rotation,  314;  standard  solution, 
164. 

Iodine  tests  in  starch  hydrolysis,  176. 


Jaggery,  155. 

Japanese  glucose,  211. 

Jellet-Cornu  prism,  19. 

Jellies,  232. 

Juice,  beet,  146;  cane,  114;  clarifying 
cane,  125 ;  clarifying  beet,  146 ;  diffu- 
sion, 145;  extraction,  115;  filter  press, 
127;  sampling,  124,  141;  scums,  127 ; 
unripe  cane,  122,  140;  weight  deter- 
mination, 138. 

Jujube  paste,  229. 

Kenricks'  tartrates  method,  273. 

Lactose  (see  milk  sugar) ,  222. 

Lamps,  for  saccharimeters,  52 ;  acetylene, 
52;  electric,  52;  gas,  52;  kerosene, 
52;  Welsbach,  52. 

Lamps,  polariscope  (sodium),  13,  50; 
Landolt,  50;  Laurent,  50,  68;  new 
form,  51 ;  Wiley,  50. 

Landolt,  2,  19,  25,  32,  36,  262. 

Landolt-Lippich  polariscope  (see  Lip- 
pich). 

Laurent's  polariscope,  22;  manipulation, 
68  ;  normal  weight,  30. 

Leach's  methods,  226,  232. 

Le  Bel  (see  Van't  Hoff). 

Lemon  oil,  271 ;  variations,  271 ;  adul- 
terants, 271,  272;  terpeneless,  272. 

Levulose,  determination,  227;  from  raf- 
finose,  108 ;  sucrose,  103 ;  multi- 
rotation,  251 ;  specific  rotation,  226. 

Light,  beam, 6;  color,  6;  complementary, 
10 ;  compound,  7,  9;  of  D  line,  n,  30; 
homogeneous  (monochromatic),  7,  9; 
intensity,  4,  8,  30;  mean  yellow,  18 ; 
optical  centre,  30 ;  optically  pure,  30 ; 
plane  of  polarization,  7 ;  plane  polar- 
ized, 4,  8;  plane  of  vibration,  7;  re- 
fraction, 22 ;  ray,  6 ;  rotary  dispersion, 
17,  32;  rotation,  9;  sodium,  9;  total 
extinction,  9 ;  undulatory  theory,  5 ; 
waves  (vibrations) ,  6  ;  white,  9. 

Light  factor,  258. 

Light  filter  (see  ray  filter). 

Limonene,  268. 

Linalool,  268. 

Lippich  polariscope,  25,  73;  manipula* 
tion,  71. 

Lippich  ray  filter,  11,72,  259. 


INDEX 


Losses  in  manufacture,  cane  sugar,  139 ; 
chemical,  140;  beet,  151;  mechanical, 
140;  milk  sugar,  223;  refinery,  159. 

Maceration,  115  ;  determination  percent- 
age, 123. 

Malt  preparations,  197. 

Maltose,  102;  by  acid  hydrolysis,  175, 
199 ;  by  diastase  hydrolysis,  174,  199 ; 
hydrolysis,  102,  175;  in  glucose,  192; 
determination  with  lactose,  224;  spe- 
cific rotation,  314;  table  for  Fehling 
determination,  304;  table  for  starch 
hydrolysis,  307. 

Maple  sugar,  227. 

Massecuite,  132. 

Mean  yellow  light,  17. 

Mechanical  filter,  146. 

Meladura,  128. 

Melter,  156. 

Menthol,  269. 

Menthone,  271. 

Midzu-ame,  211. 

Milk  sugar,  222;  manufacture,  223;  de- 
termination, 224;  separation  from 
maltose,  224. 

Millar  (see  Brown). 

Milliliter,  39. 

Mills,  cane,  114. 

Mitscherlich's  polariscope,  15. 

Mohr  cubic  centimeter,  40,  56,  58. 

Moisture  in  raw  sugars,  88,  152. 

Molasses,  beet,  148;  cane,  101,  103; 
drying,  152,  153;  firs',  134;  second, 
139;  sugars  (second  sugars),  135. 

Molecular  rotation,  249. 

Montgolfier's  yellow  light,  19. 

Morris  (see  Brown). 

Multirotation,  249. 

Muscovado  sugar,  87,  129. 

Neutralize!-,  205. 

Neutralizing,       glucose       manufacture, 

205. 
Nicol  prism,  3;  cleaning  48  ;  crossed,  4; 

effect  on  light  intensity,  4 ;  "  half,"  78  ; 

parallel,  4. 
Nicotine,    determination,    266;    specific 

rotation,  247. 
Normal     weight,     29;      dextrose,     231; 

Duboscq,  31 ;  lactose,  224 ;  Laurent,  30 ; 


United  States  standard,  46;  Ventzke, 
35,  46;  Wild,  31; 
Note  taking,  64 ;  blanks,  65. 

Open  kettle  sugar,  87,  129. 
Opposite  phase,  6. 
Optic  axis,  2. 
Optical  analysis,  i. 
Optical  centre,  30. 
Optical  isomerism,  238. 
Optically  active  bodies,  i,  10. 
Optically  pure  light,  30.^         , 
Ordinary  ray,  3. 
Osmose  process,  148. 
O'Sullivan,    221;     density    factor,    185; 
Fehling  method,  169. 

Pasteur's  researches,  i. 

Pentoses,  235,  240,  251. 

Pinene,  267. 

Plane  of  polarization,  7. 

Plane  of  vibration,  7. 

Plane  polarized  light,  4,  8. 

Polariscope,  5 ;  care,  48 ;  Duboscq 
(rotatometer),  19;  essential  parts,  14; 
Landolt-Lippich,  25;  manipulation, 
71 ;  Laurent,  22  ;  manipulation,  68  ; 
Mitscherlich,  15;  transition-tint  (Robi- 
quet),  18;  Wild  (polaristrobometer), 
26,  31 ;  manipulation,  7. 

Polariscope  tubes,  15,  39 ;  commercial 
type,  43  ;  control  tube,  41 ;  control-tube 
manipulation,  94;  for  inversion,  93; 
jacketed,  93;-  Landolt's,  43,  92;  Lau- 
rent, 43,  92;  Pellet's,  94. 

Polaristrobometer  (see  Wild  polari- 
scope). , 

Polarizer,  8. 

Polarization  formulae,  12. 

Polarization  of  commercial  sugars,  87. 

Preserves,  232. 

Prisms,  Jellet-Cornu,  19;  Nicol,  3. 

Pulegone,  271. 

Purity  (see  quotient  of  purity) . 

Pyknometer,  189. 

Quartz,  rotation,  i,  16;  rotary  dispersion, 
17,32;  specific  rotation,  30;  tempera- 
ture effect  on  rotation,  45. 

Quartz  plates,  for  standardizing,  45; 
Laurent  half-shade,  23;  standard,  41 ; 
transition-tint,  17. 


INDEX 


319 


Quartz-wedge  compensator,  32 ;  double, 
36 ;  Martens's,  36. 

Quinine,  262. 

Quotient  of  purity ,"116;  apparent,  153; 
beet  products,  153;  refinery  method, 
120;  Weisberg's  method,  121. 

Racemic  acid,  241. 

Racemic  compounds,  238 ;  resolution, 
243 ;  symbolized,  240. 

Radiator,  170. 

Raffinose,  108 ;  determination,  108 ; 
hydrolysis,  109 ;  occurrence,  108,  149. 

Raw  sugars,  155 ;  sampling,  85. 

Ray  filter,  bichromate,  73,  77 ;  brown 
glass,  78  ;  Lippich,  72,  73. 

Recording  gauges,  143. 

Refinery  losses,  159. 

Refinery  methods,  155. 

Rotation,  absolute  specific,  245 ;  funda- 
mental laws,  10 ;  relation  to  molecule, 
249;  specific,  n,  19;  standard  tem- 
perature, 13;  very  accurate  determina- 
tions, 13. 

Rotatory  power,  specific,  n. 

Saccharimeter,  28 ;  care,  48 ;  double- 
wedge,  37,  86  ;  Duboscq,  30,  31 ; 
errors,  39 ;  Fric,  37 ;  half-shade  (see 
Schmidt  and  Hansch)  ;  installation, 
48  ;  Laurent,  30,  68  ;  light  factor,  258  ; 
Peters,  36 ;  quartz-wedge,  31 ;  Schmidt 
and  Hansch,  35;  Soleil-Duboscq,  33, 
85;  Soleil-Ventzke-Scheibler,  34,  83; 
standardizing,  41,45,46;  triple-shade, 

36,  78;   United   States   standard,   46; 
Wild,  26,  31,  73. 

Saccharimeter   scales,    illumination,   35, 

37,  48,  60;  ivory,  36;  nickelin,  36;  on 
quartz,  37. 

Saccharimeter  graduation,  28,  29,  31,  35, 
46,  47,  60,  78,  100,  259. 

Saline  coefficient,  151;  cane,  113. 

Sampling  juice,  124 ;  molasses,  88 ;  raw 
sugar,  87;  in  sugarhouse,  141. 

Scales,  illumination,  35,  37, 48,  60 ;  polari- 
scope,  n, 60, 71 ;  readings, 60, 69, 71, 86 ; 
Saccharimeter,  28,  36,  37 ;  vernier,  61. 

Scheibler,  double  dilution,  97 ;  improve- 
ments on  saccharimeters,  34;  mois- 
ture in  starch,  216;  ash  method,  151. 


.Second  grain,  132.  .    . 

Seedling  cane,  112. 

Seed  selection  of  beets,  144. 

Sensitive  tint,  33,  83. 

Shredder,  114. 

Size  compounds,  218. 

Sodium  light,  9,  n,  30;  filtered,  n;  op- 
tical centre,  n  ;  spectrally  purified,  n  ; 
wave  length,  n  (see  lamps). 

Solvent,  effect  on  rotation,  12,  245.         •>- 

Soxhlet  tube,  169. 

Soxhlet,  Fehling  solution,  161. 

Special  laboratory  apparatus,  54. 

Specific  gravity,  186;  by  Brix  spindle, 
118  ;  calculations,  190 ,  factors,  185, 191 ; 
by  pyknometer,  189 ;  by  Wesphal  bal- 
ance, 186. 

Specific  rotatory  power,  n,  19;  absolute, 
245  ;  effect  of  salts,  etc.,  247  ;  formulae, 
12;  molecular,  249;  solvent  effect,  12, 
244;  table,  314;  temperature  effect,  12, 
247 ;  very  accurate  determinations, 

13- 

Speed  of  hydrolysis,  252,  254. 

Standards,  light,  u,  19,  30;  sacchari- 
metric,  30,  46. 

Starch,  173;  acid,  214;  alkalai,  214; 
chemistry,  174 ;  corn,  178,  202 ;  fluidity 
(viscosity),  215  ;  hydrolysis,  174  ;  iodine 
tests,  176;  manufacture,  176, 202 ;  mois- 
ture in,  216;  paddling,  213;  potato. 
177 ;  thin  boiling,  177,  214 ;  wheat,  178. 

Starch  determinations,  177  ;  diastase, 
180;  Hibbard,  181;  Sachsse,  180. 

Steffen's  molasses  process,  149. 

Stock     in     process,     137;      calculation, 

139. 
Sucrose,     chemistry,     101  ;     chemically 

pure,  95;  inversion  (hydrolysis),  103; 

per  cent  by  density  (Brix  table),  285; 

pipette,  118 ;  specific  rotation,  314. 
Sugar,  chemistry,  101 ;   commercial,  87; 

effect   on   polarized    light,   9;    export 

(beet),  in,  133;  grape, 200;  hydrolysis, 

101,251;  in  urine,  236;  multirotation, 

249. 

Sulphites  in  glucose,  207. 
Sulphuring,  beet  juice,  146,  147 ;    cane 

juice,  125. 
Synthetic    compounds,     inactive,     243; 

made  active,  243. 


320 


INDEX 


Tables,  Brix,  285;  Beaume,  285;  Brix 
temperature  correction,  295 ;  carbo- 
hydrates of  acid-hydrolyzed  starch, 
307;  cupric-reducing  power  of  acid- 
hydrolyzed  starch,  307;  Defren's 
copper  oxide  equivalents,  304  ;  density 
of  sugar  solutions,  285;  density  of 
water,  310;  density  factors  for  hydro- 
lyzed  starch,  195 ;  Herzfeld's  double 
polarization  factors,  107;  Herzfeld's 
Fehiing  invert  sugar  equivalents,  312, 
313 ;  Saare's  moisture  in  starch,  217 ; 
Schmitz  sucrose  solution,  296 ;  Schmitz 
saccharimeter  correction,  99;  volume 
of  sugar  solutions,  311;  Weisberg's 
quotient  of  purity  correction,  154. 

Tartaric  acid,  241 ;  specific  rotation,  247, 
263. 

Tartrates,  Kenricks'  method,  273. 

Temperature,  effect  on  rotation,  n,  45, 
247 ;  effect  on  hydrolysis,  254 ;  errors 
in  saccharimetry,  43;  standard  for 
polarizing,  12,  13,  45;  standard  for 
starch  analysis,  193 ;  standard  for  sugar 
analysis,  43. 

Terebenthene  (see  pinene) . 

Terpeneol,  269. 

Terpentine  in  lemon  oil,  271 ;  specific 
rotation,  247. 

Thujone,  270. 

Tol man's  double  polarization  formulae, 
108. 

Total  solids,  by  drying,  152 ;  Brix  spindle, 
116  ;  Weisberg's  method,  153. 

Transition  tint,  17. 

Transition-tint  plate,  16. 

Treacle,  157. 

Trier,  88. 


Undulation  (see  wave). 
Undulatory  theory,  5. 
Urine,  sugar  in,  236;  creatinin  in,  236; 
polarization,  237. 

Van't  Hoff-Le  Bel  theory,  i,  238,  249. 
Vernier  scale,  61 ;    method  of  reading, 

61. 
Viscosity  of  cane  juices,  122;  starches, 

214  ;  dextrins,  220. 
Viscosimeter,  215. 

Water  for  polarimetry,  55  ;  density  table, 
310. 

Wave,  6. 

Wave  length,  67;  half,  6;  sodium  light, 
ii. 

Weber  and  McPherson,  glucose  correc- 
tion, 107. 

Wedge  (see  quartz  wedge). 

Weisberg,  purity  method,  121 ;  correc- 
tion table,  154. 

Whey,  222. 

White  sugar,  125. 

Wiley,  double  dilution,  97;  glucose 
research,  183  ;  lactose  clarification,  224 ; 
levulose  determination,  227 ;  starch 
determination,  80;  temperature  correc- 
tion, 44. 

Xylose,  235,  251. 

Yellow  light,  9;  mean,  18,  19. 

Zero  error,  42,  44 ;  affected  by  tempera- 
ture, 44;  when  ignored,  45. 


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